Generation of a computerized bone model representative of a pre-degenerated state and useable in the design and manufacture of arthroplasty devices

ABSTRACT

A method of generating a computerized bone model representative of at least a portion of a patient bone in a pre-degenerated state. The method includes: generating at least one image of the patient bone in a degenerated state; identifying a reference portion associated with a generally non-degenerated portion of the patient bone; identifying a degenerated portion associated with a generally degenerated portion of the patient bone; and using information from at least one image associated with the reference portion to modify at least one aspect associated with at least one image associated the generally degenerated portion. The method may further include employing the computerized bone model representative of the at least a portion of the patient bone in the pre-degenerated state in defining manufacturing instructions for the manufacture of a customized arthroplasty jig.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of U.S.application Ser. No. 13/923,093 filed Jun. 20, 2013, which applicationis a divisional application of U.S. application Ser. No. 12/111,924filed Apr. 29, 2008, now U.S. Pat. No. 8,480,679, which application ishereby incorporated by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to systems and methods for manufacturingcustomized surgical devices. More specifically, the present inventionrelates to automated systems and methods for manufacturing customizedarthroplasty jigs.

BACKGROUND OF THE INVENTION

Over time and through repeated use, bones and joints can become damagedor worn. For example, repetitive strain on bones and joints (e.g.,through athletic activity), traumatic events, and certain diseases(e.g., arthritis) can cause cartilage in joint areas, which normallyprovides a cushioning effect, to wear down. When the cartilage wearsdown, fluid can accumulate in the joint areas, resulting in pain,stiffness, and decreased mobility.

Arthroplasty procedures can be used to repair damaged joints. During atypical arthroplasty procedure, an arthritic or otherwise dysfunctionaljoint can be remodeled or realigned, or an implant can be implanted intothe damaged region. Arthroplasty procedures may take place in any of anumber of different regions of the body, such as a knee, a hip, ashoulder, or an elbow.

One type of arthroplasty procedure is a total knee arthroplasty (“TKA”),in which a damaged knee joint is replaced with prosthetic implants. Theknee joint may have been damaged by, for example, arthritis (e.g.,severe osteoarthritis or degenerative arthritis), trauma, or a raredestructive joint disease. During a TKA procedure, a damaged portion inthe distal region of the femur may be removed and replaced with a metalshell, and a damaged portion in the proximal region of the tibia may beremoved and replaced with a channeled piece of plastic having a metalstem. In some TKA procedures, a plastic button may also be added underthe surface of the patella, depending on the condition of the patella.

Implants that are implanted into a damaged region may provide supportand structure to the damaged region, and may help to restore the damagedregion, thereby enhancing its functionality. Prior to implantation of animplant in a damaged region, the damaged region may be prepared toreceive the implant. For example, in a knee arthroplasty procedure, oneor more of the bones in the knee area, such as the femur and/or thetibia, may be treated (e.g., cut, drilled, reamed, and/or resurfaced) toprovide one or more surfaces that can align with the implant and therebyaccommodate the implant.

Accuracy in implant alignment is an important factor to the success of aTKA procedure. A one- to two-millimeter translational misalignment, or aone- to two-degree rotational misalignment, may result in imbalancedligaments, and may thereby significantly affect the outcome of the TKAprocedure. For example, implant misalignment may result in intolerablepost-surgery pain, and also may prevent the patient from having full legextension and stable leg flexion.

To achieve accurate implant alignment, prior to treating (e.g., cutting,drilling, reaming, and/or resurfacing) any regions of a bone, it isimportant to correctly determine the location at which the treatmentwill take place and how the treatment will be oriented. In some methods,an arthroplasty jig may be used to accurately position and orient afinishing instrument, such as a cutting, drilling, reaming, orresurfacing instrument on the regions of the bone. The arthroplasty jigmay, for example, include one or more apertures and/or slots that areconfigured to accept such an instrument.

A system and method has been developed for producing customizedarthroplasty jigs configured to allow a surgeon to accurately andquickly perform an arthroplasty procedure that restores thepre-deterioration alignment of the joint, thereby improving the successrate of such procedures. Specifically, the customized arthroplasty jigsare indexed such that they matingly receive the regions of the bone tobe subjected to a treatment (e.g., cutting, drilling, reaming, and/orresurfacing). The customized arthroplasty jigs are also indexed toprovide the proper location and orientation of the treatment relative tothe regions of the bone. The indexing aspect of the customizedarthroplasty jigs allows the treatment of the bone regions to be donequickly and with a high degree of accuracy that will allow the implantsto restore the patient's joint to a generally pre-deteriorated state.However, the system and method for generating the customized jigs oftenrelies on a human to “eyeball” bone models on a computer screen todetermine configurations needed for the generation of the customizedjigs. This is “eyeballing” or manual manipulation of the bone models onthe computer screen is inefficient and unnecessarily raises the time,manpower and costs associated with producing the customized arthroplastyjigs. Furthermore, a less manual approach may improve the accuracy ofthe resulting jigs.

There is a need in the art for a system and method for reducing thelabor associated with generating customized arthroplasty jigs. There isalso a need in the art for a system and method for increasing theaccuracy of customized arthroplasty jigs.

SUMMARY

Preoperative assessment of bone loss is advantageous for prosthesisdesign, for example, to reduce the likelihood of prosthesis looseningand to provide a more reliable bone restoration method for preoperativeimplant design, thereby improving the success rate for such proceduressuch as total knee arthroplasty (“TKA”) and partial knee arthroplasty(e.g., a unicompartment knee arthroplasty) and providing apatient-specific bone restoration method to fit an individual patient'sknee features.

The current available joint reconstruction and replacement surgeries,including knee, ankle, hip, shoulder or elbow arthroplasty, are mainlybased on standard guidelines and methods for acceptable performance.Taking this into account, the positioning and orientation of thearthroplasty work on a joint is based on standard values for orientationrelative to the biomechanical axes, such as flexion/extension,varus/valgus, and range of motion.

One of the surgical goals of joint replacement/reconstruction should beto achieve a certain alignment relative to a load axes. However, theconventional standards are based on static load analysis and thereforemay not be able to provide an optimal joint functionality for adoptingindividual knee features of OA patients. The methods disclosed hereinprovide a kinetic approach for bone restoration, properly balancing theunconstrained joint and ligaments surrounding the joint, and resultingin a placement of a prosthetic implant that generally restores thepatient's knee to a generally pre-degenerated state.

In one embodiment, the result of the bone restoration process disclosedherein is a TKA or partial knee arthroplasty procedure that generallyreturns the knee to its pre-degenerated state whether thatpre-degenerated state is naturally varus, valgus or neutral. In otherwords, if the patient's knee was naturally varus, valgus or neutralprior to degenerating, the surgical procedure will result in a knee thatis generally restored to that specific natural pre-degeneratedalignment, as opposed to simply making the knee have an alignment thatcorresponds to the mechanical axis, as is the common focus and result ofmost, if not all, arthroplasty procedures known in the art.

Disclosed herein is a method of generating a restored bone modelrepresentative of at least a portion of a patient bone in apre-degenerated state. In one embodiment, the method includes:determining reference information from a reference portion of adegenerated bone model representative of the at least a portion of thepatient bone in a degenerated state; and using the reference informationto restore a degenerated portion of the degenerated bone model into arestored portion representative of the degenerated portion in thepre-degenerated state. In one embodiment, the method further includesemploying the restored bone model in defining manufacturing instructionsfor the manufacture of a customized arthroplasty jig.

Also disclosed herein is a customized arthroplasty jig manufacturedaccording to the above-described method. In one embodiment, thecustomized arthroplasty jig is configured to facilitate a prostheticimplant restoring a patient joint to a natural alignment. The prostheticimplant may be for a total joint replacement or partial jointreplacement. The patient joint may be a variety of joints, including,but not limited to, a knee joint.

Disclosed herein is a method of generating a computerized bone modelrepresentative of at least a portion of a patient bone in apre-degenerated state. In one embodiment, the method includes:generating at least one image of the patient bone in a degeneratedstate; identifying a reference portion associated with a generallynon-degenerated portion of the patient bone; identifying a degeneratedportion associated with a generally degenerated portion of the patientbone; and using information from at least one image associated with thereference portion to modify at least one aspect associated with at leastone image associated the generally degenerated portion. In oneembodiment, the method may further include employing the computerizedbone model representative of the at least a portion of the patient bonein the pre-degenerated state in defining manufacturing instructions forthe manufacture of a customized arthroplasty jig.

Also disclosed herein is a customized arthroplasty jig manufacturedaccording to the above-described method. In one embodiment, thecustomized arthroplasty jig is configured to facilitate a prostheticimplant restoring a patient joint to a natural alignment. The prostheticimplant may be for a total joint replacement or partial jointreplacement. The patient joint may be a variety of joints, including,but not limited to, a knee joint.

Disclosed herein is a method of generating a computerized bone modelrepresentative of at least a portion of a first patient bone in apre-degenerated state. In one embodiment, the method includes:generating at least one image of the first patient bone in a degeneratedstate; identifying a reference portion associated with a generallynon-degenerated portion of a second patient bone; identifying adegenerated portion associated with a generally degenerated portion ofthe first patient bone; and using information from at least one imageassociated with the reference portion to modify at least one aspectassociated with at least one image associated the generally degeneratedportion. In one embodiment, the method may further include employing thecomputerized bone model representative of the at least a portion of thefirst patient bone in the pre-degenerated state in definingmanufacturing instructions for the manufacture of a customizedarthroplasty jig.

Also disclosed herein is a customized arthroplasty jig manufacturedaccording to the above-described method. In one embodiment, thecustomized arthroplasty jig is configured to facilitate a prostheticimplant restoring a patient joint to a natural alignment. The prostheticimplant may be for a total joint replacement or partial jointreplacement. The patient joint may be a variety of joints, including,but not limited to, a knee joint.

Disclosed herein is a method of generating a computerized bone modelrepresentative of at least a portion of a first patient bone in apre-degenerated state, wherein the first patient bone is part of a firstpatient joint. In one embodiment, the method includes: identifying asecond patient bone of a second joint, wherein the second bone is agenerally symmetrical mirror image of the first patient bone; generatinga plurality of images of the second patient bone when the second patientbone is in a generally non-degenerated state; mirroring the plurality ofimages to reverse the order of the plurality images; and compiling theplurality of images in the reversed order to form the computerized bonemodel representative of the at least a portion of the first patientbone. In one embodiment, the method may further include employing thecomputerized bone model representative of the at least a portion of thefirst patient bone in the pre-degenerated state in definingmanufacturing instructions for the manufacture of a customizedarthroplasty jig.

Also disclosed herein is a customized arthroplasty jig manufacturedaccording to the above-described method. In one embodiment, thecustomized arthroplasty jig is configured to facilitate a prostheticimplant restoring a patient joint to a natural alignment. The prostheticimplant may be for a total joint replacement or partial jointreplacement. The patient joint may be a variety of joints, including,but not limited to, a knee joint.

While multiple embodiments are disclosed, still other embodiments of thepresent invention will become apparent to those skilled in the art fromthe following detailed description, which shows and describesillustrative embodiments of the invention. As will be realized, theinvention is capable of modifications in various aspects, all withoutdeparting from the spirit and scope of the present invention.Accordingly, the drawings and detailed description are to be regarded asillustrative in nature and not restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic diagram of a system for employing the automatedjig production method disclosed herein.

FIGS. 1B-1E are flow chart diagrams outlining the jig production methoddisclosed herein.

FIGS. 1F and 1G are, respectively, bottom and top perspective views ofan example customized arthroplasty femur jig.

FIGS. 1H and 1I are, respectively, bottom and top perspective views ofan example customized arthroplasty tibia jig.

FIG. 2 is a diagram generally illustrating a bone restoration processfor restoring a 3D computer generated bone model into a 3D computergenerated restored bone model.

FIG. 3A is a coronal view of a distal or knee joint end of a femurrestored bone model.

FIG. 3B is an axial view of a distal or knee joint end of a femurrestored bone model.

FIG. 3C is a coronal view of a proximal or knee joint end of a tibiarestored bone model.

FIG. 3D represents the femur and tibia restored bone models in the viewsdepicted in FIGS. 3A and 3C positioned together to form a knee joint.

FIG. 3E represents the femur and tibia restored bone models in the viewsdepicted in FIGS. 3B and 3C positioned together to form a knee joint.

FIG. 3F is a sagittal view of the femoral medial condyle ellipse and,more specifically, the N1 slice of the femoral medial condyle ellipse astaken along line N1 in FIG. 3A.

FIG. 3G is a sagittal view of the femoral lateral condyle ellipse and,more specifically, the N2 slice of the femoral lateral condyle ellipseas taken along line N2 in FIG. 3A.

FIG. 3H is a sagittal view of the femoral medial condyle ellipse and,more specifically, the N3 slice of the femoral medial condyle ellipse astaken along line N3 in FIG. 3B.

FIG. 3I is a sagittal view of the femoral lateral condyle ellipse and,more specifically, the N4 slice of the femoral lateral condyle ellipseas taken along line N4 in FIG. 3B.

FIG. 4A is a sagittal view of the lateral tibia plateau with the lateralfemur condyle ellipse of the N1 slice of FIG. 3F superimposed thereon.

FIG. 4B is a sagittal view of the medial tibia plateau with the lateralfemur condyle ellipse of the N2 slice of FIG. 3G superimposed thereon.

FIG. 4C is a top view of the tibia plateaus of a restored tibia bonemodel.

FIG. 4D is a sagittal cross section through a lateral tibia plateau ofthe restored bone model 28B of FIG. 4C and corresponding to the N3 imageslice of FIG. 3B.

FIG. 4E is a sagittal cross section through a medial tibia plateau ofthe restored bone model of FIG. 4C and corresponding to the N4 imageslice of FIG. 3B.

FIG. 4F is a posterior-lateral perspective view of femur and tibia bonemodels forming a knee joint.

FIG. 4G is a posterior-lateral perspective view of femur and tibiarestored bone models forming a knee joint.

FIG. 5A is a coronal view of a femur bone model.

FIG. 5B is a coronal view of a tibia bone model.

FIG. 5C1 is an N2 image slice of the medial condyle as taken along theN2 line in FIG. 5A.

FIG. 5C2 is the same view as FIG. 5C1, except illustrating the need toincrease the size of the reference information prior to restoring thecontour line of the N2 image slice.

FIG. 5C3 is the same view as FIG. 5C1, except illustrating the need toreduce the size of the reference information prior to restoring thecontour line of the N2 image slice.

FIG. 5D is the N2 image slice of FIG. 5C1 subsequent to restoration.

FIG. 5E is a sagittal view of the medial tibia plateau along the N4image slice, wherein damage to the plateau is mainly in the posteriorregion.

FIG. 5F is a sagittal view of the medial tibia plateau along the N4image slice, wherein damage to the plateau is mainly in the anteriorregion.

FIG. 5G is the same view as FIG. 5E, except showing the reference sidefemur condyle vector extending through the anterior highest point of thetibia plateau.

FIG. 5H is the same view as FIG. 5F, except showing the reference sidefemur condyle vector extending through the posterior highest point ofthe tibia plateau.

FIG. 5I is the same view as FIG. 5G, except showing the anterior highestpoint of the tibia plateau restored.

FIG. 5J is the same view as FIG. 5H, except showing the posteriorhighest point of the tibia plateau restored.

FIG. 5K is the same view as FIG. 5G, except employing reference vectorV₁ as opposed to U₁.

FIG. 5L is the same view as FIG. 5H, except employing reference vectorV₁ as opposed to U₁.

FIG. 5M is the same view as FIG. 5I, except employing reference vectorV₁ as opposed to U₁.

FIG. 5N is the same view as FIG. 5J, except employing reference vectorV₁ as opposed to U₁.

FIG. 6A is a sagittal view of a femur restored bone model illustratingthe orders and orientations of imaging slices (e.g., MRI slices, CTslices, etc.) forming the femur restored bone model.

FIG. 6B is the distal images slices 1-5 taken along section lines 1-5 ofthe femur restored bone model in FIG. 6A.

FIG. 6C is the coronal images slices 6-8 taken along section lines 6-8of the femur restored bone model in FIG. 6A.

FIG. 6D is a perspective view of the distal end of the femur restoredbone model.

FIG. 7 is a table illustrating how OA knee conditions may impact thelikelihood of successful bone restoration.

FIGS. 8A-8D are various views of the tibia plateau with reference torestoration of a side thereof.

FIGS. 9A and 9B are, respectively, coronal and sagittal views of therestored bone models.

FIG. 10A is a diagram illustrating the condition of a patient's rightknee, which is in a deteriorated state, and left knee, which isgenerally healthy.

FIG. 10B is a diagram illustrating two options for creating a restoredbone model for a deteriorated right knee from image slices obtained froma healthy left knee.

DETAILED DESCRIPTION

Disclosed herein are customized arthroplasty jigs 2 and systems 4 for,and methods of, producing such jigs 2. The jigs 2 are customized to fitspecific bone surfaces of specific patients. Depending on the embodimentand to a greater or lesser extent, the jigs 2 are automatically plannedand generated and may be similar to those disclosed in these three U.S.patent applications: U.S. patent application Ser. No. 11/656,323 to Parket al., titled “Arthroplasty Devices and Related Methods” and filed Jan.19, 2007; U.S. patent application Ser. No. 10/146,862 to Park et al.,titled “Improved Total Joint Arthroplasty System” and filed May 15,2002; and U.S. patent Ser. No. 11/642,385 to Park et al., titled“Arthroplasty Devices and Related Methods” and filed Dec. 19, 2006. Thedisclosures of these three U.S. patent applications are incorporated byreference in their entireties into this Detailed Description.

a. Overview of System and Method for Manufacturing CustomizedArthroplasty Cutting Jigs

For an overview discussion of the systems 4 for, and methods of,producing the customized arthroplasty jigs 2, reference is made to FIGS.1A-1E. FIG. 1A is a schematic diagram of a system 4 for employing theautomated jig production method disclosed herein. FIGS. 1B-1E are flowchart diagrams outlining the jig production method disclosed herein. Thefollowing overview discussion can be broken down into three sections.

The first section, which is discussed with respect to FIG. 1A and[blocks 100-125] of FIGS. 1B-1E, pertains to an example method ofdetermining, in a three-dimensional (“3D”) computer model environment,saw cut and drill hole locations 30, 32 relative to 3D computer modelsthat are termed restored bone models 28. The resulting “saw cut anddrill hole data” 44 is referenced to the restored bone models 28 toprovide saw cuts and drill holes that will allow arthroplasty implantsto generally restore the patient's joint to its pre-degenerated state.In other words, the patient's joint will be restored to its naturalalignment prior to degeneration. Thus, where the patient'spre-degenerated joint had a certain degree of valgus, the saw cuts anddrill holes will allow the arthroplasty implants to generally restorethe patient's joint to that degree of valgus. Similarly, where thepatient's pre-degenerated joint had a certain degree of varus, the sawcuts and drill holes will allow the arthroplasty implants to generallyrestore the patient's joint to that degree of varus, and where thepatient's pre-degenerated joint was neutral, the saw cuts and drillholes will allow the arthroplasty implants to generally restore thepatient's joint to neutral.

The second section, which is discussed with respect to FIG. 1A and[blocks 100-105 and 130-145] of FIGS. 1B-1E, pertains to an examplemethod of importing into 3D computer generated jig models 38 3D computergenerated surface models 40 of arthroplasty target areas 42 of 3Dcomputer generated arthritic models 36 of the patient's joint bones. Theresulting “jig data” 46 is used to produce a jig customized to matinglyreceive the arthroplasty target areas of the respective bones of thepatient's joint.

The third section, which is discussed with respect to FIG. 1A and[blocks 150-165] of FIG. 1E, pertains to a method of combining orintegrating the “saw cut and drill hole data” 44 with the “jig data” 46to result in “integrated jig data” 48. The “integrated jig data” 48 isprovided to the CNC machine 10 for the production of customizedarthroplasty jigs 2 from jig blanks 50 provided to the CNC machine 10.The resulting customized arthroplasty jigs 2 include saw cut slots anddrill holes positioned in the jigs 2 such that when the jigs 2 matinglyreceive the arthroplasty target areas of the patient's bones, the cutslots and drill holes facilitate preparing the arthroplasty target areasin a manner that allows the arthroplasty joint implants to generallyrestore the patient's joint line to its pre-degenerated state. In otherwords, the customized arthroplasty jigs 2 facilitate preparing thepatient's bone in a manner that allows the arthroplasty joint implantsto restore the patient's joint to a natural alignment that correspondsto the patient's specific pre-degenerated alignment, whether thatspecific pre-degenerated alignment was valgus, varus or neutral.

As shown in FIG. 1A, the system 4 includes a computer 6 having a CPU 7,a monitor or screen 9 and an operator interface controls 11. Thecomputer 6 is linked to a medical imaging system 8, such as a CT or MRImachine 8, and a computer controlled machining system 10, such as a CNCmilling machine 10.

As indicated in FIG. 1A, a patient 12 has a joint 14 (e.g., a knee,elbow, ankle, wrist, hip, shoulder, skull/vertebrae orvertebrae/vertebrae interface, etc.) to be totally replaced (e.g., TKA),partially replaced (e.g., partial or compartmentalized replacement),resurfaced, or otherwise treated. The patient 12 has the joint 14scanned in the imaging machine 8. The imaging machine 8 makes aplurality of scans of the joint 14, wherein each scan pertains to a thinslice of the joint 14.

As can be understood from FIG. 1B, the plurality of scans is used togenerate a plurality of two-dimensional (“2D”) images 16 of the joint 14[block 100]. Where, for example, the joint 14 is a knee 14, the 2Dimages will be of the femur 18 and tibia 20. The imaging may beperformed via CT or MRI. In one embodiment employing MRI, the imagingprocess may be as disclosed in U.S. patent application Ser. No.11/946,002 to Park, which is entitled “Generating MRI Images Usable ForThe Creation Of 3D Bone Models Employed To Make Customized ArthroplastyJigs,” was filed Nov. 27, 2007 and is incorporated by reference in itsentirety into this Detailed Description.

As can be understood from FIG. 1A, the 2D images are sent to thecomputer 6 for creating computer generated 3D models. As indicated inFIG. 1B, in one embodiment, point P is identified in the 2D images 16[block 105]. In one embodiment, as indicated in [block 105] of FIG. 1A,point P may be at the approximate medial-lateral and anterior-posteriorcenter of the patient's joint 14. In other embodiments, point P may beat any other location in the 2D images 16, including anywhere on, nearor away from the bones 18, 20 or the joint 14 formed by the bones 18,20.

As described later in this overview, point P may be used to locate thecomputer generated 3D models 22, 28, 36 created from the 2D images 16and to integrate information generated via the 3D models. Depending onthe embodiment, point P, which serves as a position and/or orientationreference, may be a single point, two points, three points, a point plusa plane, a vector, etc., so long as the reference P can be used toposition and/or orient the 3D models 22, 28, 36 generated via the 2Dimages 16.

As shown in FIG. 1C, the 2D images 16 are employed to create computergenerated 3D bone-only (i.e., “bone models”) 22 of the bones 18, 20forming the patient's joint 14 [block 110]. The bone models 22 arelocated such that point P is at coordinates (X_(0-j), Y_(0-j), Z_(0-j))relative to an origin (X₀, Y₀, Z₀) of an X-Y-Z axis [block 110]. Thebone models 22 depict the bones 18, 20 in the present deterioratedcondition with their respective degenerated joint surfaces 24, 26, whichmay be a result of osteoarthritis, injury, a combination thereof, etc.

Computer programs for creating the 3D computer generated bone models 22from the 2D images 16 include: Analyze from AnalyzeDirect, Inc.,Overland Park, Kans.; Insight Toolkit, an open-source software availablefrom the National Library of Medicine Insight Segmentation andRegistration Toolkit (“ITK”), www.itk.org; 3D Slicer, an open-sourcesoftware available from www.slicer.org; Mimics from Materialise, AnnArbor, Mich.; and Paraview available at www.paraview.org.

As indicated in FIG. 1C, the 3D computer generated bone models 22 areutilized to create 3D computer generated “restored bone models” or“planning bone models” 28 wherein the degenerated surfaces 24, 26 aremodified or restored to approximately their respective conditions priorto degeneration [block 115]. Thus, the bones 18, 20 of the restored bonemodels 28 are reflected in approximately their condition prior todegeneration. The restored bone models 28 are located such that point Pis at coordinates (X_(0-j), Y_(0-j), Z_(0-j)) relative to the origin(X₀, Y₀, Z₀). Thus, the restored bone models 28 share the sameorientation and positioning relative to the origin (X₀, Y₀, Z₀) as thebone models 22.

In one embodiment, the restored bone models 28 are manually created fromthe bone models 22 by a person sitting in front of a computer 6 andvisually observing the bone models 22 and their degenerated surfaces 24,26 as 3D computer models on a computer screen 9. The person visuallyobserves the degenerated surfaces 24, 26 to determine how and to whatextent the degenerated surfaces 24, 26 on the 3D computer bone models 22need to be modified to generally restore them to their pre-degeneratedcondition or an estimation or approximation of their pre-degeneratedstate. By interacting with the computer controls 11, the person thenmanually manipulates the 3D degenerated surfaces 24, 26 via the 3Dmodeling computer program to restore the surfaces 24, 26 to a state theperson believes to represent the pre-degenerated condition. The resultof this manual restoration process is the computer generated 3D restoredbone models 28, wherein the surfaces 24′, 26′ are indicated in anon-degenerated state. In other words, the result is restored bonemodels 28 that can be used to represent the natural, pre-degeneratedalignment and configuration of the patient's knee joint whether thatpre-degenerated alignment and configuration was varus, valgus orneutral.

In one embodiment, the above-described bone restoration process isgenerally or completely automated to occur via a processor employing themethods disclosed herein. In other words, a computer program may analyzethe bone models 22 and their degenerated surfaces 24, 26 to determinehow and to what extent the degenerated surfaces 24, 26 surfaces on the3D computer bone models 22 need to be modified to restore them to theirpre-degenerated condition or an estimation or approximation of theirpre-degenerated state. The computer program then manipulates the 3Ddegenerated surfaces 24, 26 to restore the surfaces 24, 26 to a stateintended to represent the pre-degenerated condition. The result of thisautomated restoration process is the computer generated 3D restored bonemodels 28, wherein the surfaces 24′, 26′ are indicated in anon-degenerated state. A discussion of various embodiments of theautomated restoration process employed to a greater or lesser extent bya computer is provided later in this Detailed Description.

As depicted in FIG. 1C, the restored bone models 28 are employed in apreoperative planning (“POP”) procedure to determine saw cut locations30 and drill hole locations 32 in the patient's bones that will allowthe arthroplasty joint implants, whether in the context of total jointarthroplasty or partial or compartmentalized joint arthroplasty, togenerally restore the patient's joint line to its pre-degenerative ornatural alignment [block 120].

In one embodiment, the POP procedure is a manual process, whereincomputer generated 3D implant models 34 (e.g., femur and tibia implantsin the context of the joint being a knee) and restored bone models 28are manually manipulated relative to each other by a person sitting infront of a computer 6 and visually observing the implant models 34 andrestored bone models 28 on the computer screen 9 and manipulating themodels 28, 34 via the computer controls 11. By superimposing the implantmodels 34 over the restored bone models 28, or vice versa, the jointsurfaces of the implant models 34 can be aligned or caused to correspondwith the joint surfaces of the restored bone models 28. By causing thejoint surfaces of the models 28, 34 to so align, the implant models 34are positioned relative to the restored bone models 28 such that the sawcut locations 30 and drill hole locations 32 can be determined relativeto the restored bone models 28.

In one embodiment, the POP process is generally or completely automated.For example, a computer program may manipulate computer generated 3Dimplant models 34 (e.g., femur and tibia implants in the context of thejoint being a knee) and restored bone models or planning bone models 8relative to each other to determine the saw cut and drill hole locations30, 32 relative to the restored bone models 28. The implant models 34may be superimposed over the restored bone models 28, or vice versa. Inone embodiment, the implant models 34 are located at point P′ (X_(0-k),Y_(0-k), Z_(0-k)) relative to the origin (X₀, Y₀, Z₀), and the restoredbone models 28 are located at point P (X_(0-j), Y_(0-j), Z_(0-j)). Tocause the joint surfaces of the models 28, 34 to correspond, thecomputer program may move the restored bone models 28 from point P(X_(0-j), Y_(0-j), Z_(0-j)) to point P′ (X_(0-k), Y_(0-k), Z_(0-k)), orvice versa. Once the joint surfaces of the models 28, 34 are in closeproximity, the joint surfaces of the implant models 34 may beshape-matched to align or correspond with the joint surfaces of therestored bone models 28. By causing the joint surfaces of the models 28,34 to so align, the implant models 34 are positioned relative to therestored bone models 28 such that the saw cut locations 30 and drillhole locations 32 can be determined relative to the restored bone models28.

As indicated in FIG. 1E, in one embodiment, the data 44 regarding thesaw cut and drill hole locations 30, 32 relative to point P′ (X_(0-k),Y_(0-k), Z_(0-k)) is packaged or consolidated as the “saw cut and drillhole data” 44 [block 145]. The “saw cut and drill hole data” 44 is thenused as discussed below with respect to [block 150] in FIG. 1E.

As can be understood from FIG. 1D, the 2D images 16 employed to generatethe bone models 22 discussed above with respect to [block 110] of FIG.1C are also used to create computer generated 3D bone and cartilagemodels (i.e., “arthritic models”) 36 of the bones 18, 20 forming thepatient's joint 14 [block 130]. Like the above-discussed bone models 22,the arthritic models 36 are located such that point P is at coordinates(X_(0-j), Y_(0-j), Z_(0-j)) relative to the origin (X₀, Y₀, Z₀) of theX-Y-Z axis [block 130]. Thus, the bone and arthritic models 22, 36 sharethe same location and orientation relative to the origin (X₀, Y₀, Z₀).This position/orientation relationship is generally maintainedthroughout the process discussed with respect to FIGS. 1B-1E.Accordingly, movements relative to the origin (X₀, Y₀, Z₀) of the bonemodels 22 and the various descendants thereof (i.e., the restored bonemodels 28, bone cut locations 30 and drill hole locations 32) are alsoapplied to the arthritic models 36 and the various descendants thereof(i.e., the jig models 38). Maintaining the position/orientationrelationship between the bone models 22 and arthritic models 36 andtheir respective descendants allows the “saw cut and drill hole data” 44to be integrated into the “jig data” 46 to form the “integrated jigdata” 48 employed by the CNC machine 10 to manufacture the customizedarthroplasty jigs 2.

Computer programs for creating the 3D computer generated arthriticmodels 36 from the 2D images 16 include: Analyze from AnalyzeDirect,Inc., Overland Park, Kans.; Insight Toolkit, an open-source softwareavailable from the National Library of Medicine Insight Segmentation andRegistration Toolkit (“ITK”), www.itk.org; 3D Slicer, an open-sourcesoftware available from www.slicer.org; Mimics from Materialise, AnnArbor, Mich.; and Paraview available at www.paraview.org.

Similar to the bone models 22, the arthritic models 36 depict the bones18, 20 in the present deteriorated condition with their respectivedegenerated joint surfaces 24, 26, which may be a result ofosteoarthritis, injury, a combination thereof, etc. However, unlike thebone models 22, the arthritic models 36 are not bone-only models, butinclude cartilage in addition to bone. Accordingly, the arthritic models36 depict the arthroplasty target areas 42 generally as they will existwhen the customized arthroplasty jigs 2 matingly receive thearthroplasty target areas 42 during the arthroplasty surgical procedure.

As indicated in FIG. 1D and already mentioned above, to coordinate thepositions/orientations of the bone and arthritic models 36, 36 and theirrespective descendants, any movement of the restored bone models 28 frompoint P to point P′ is tracked to cause a generally identicaldisplacement for the “arthritic models” 36 [block 135].

As depicted in FIG. 1D, computer generated 3D surface models 40 of thearthroplasty target areas 42 of the arthritic models 36 are importedinto computer generated 3D arthroplasty jig models 38 [block 140]. Thus,the jig models 38 are configured or indexed to matingly receive thearthroplasty target areas 42 of the arthritic models 36. Jigs 2manufactured to match such jig models 38 will then matingly receive thearthroplasty target areas of the actual joint bones during thearthroplasty surgical procedure.

In one embodiment, the procedure for indexing the jig models 38 to thearthroplasty target areas 42 is a manual process. The 3D computergenerated models 36, 38 are manually manipulated relative to each otherby a person sitting in front of a computer 6 and visually observing thejig models 38 and arthritic models 36 on the computer screen 9 andmanipulating the models 36, 38 by interacting with the computer controls11. In one embodiment, by superimposing the jig models 38 (e.g., femurand tibia arthroplasty jigs in the context of the joint being a knee)over the arthroplasty target areas 42 of the arthritic models 36, orvice versa, the surface models 40 of the arthroplasty target areas 42can be imported into the jig models 38, resulting in jig models 38indexed to matingly receive the arthroplasty target areas 42 of thearthritic models 36. Point P′ (X_(0-k), Y_(0-k), Z_(0-k)) can also beimported into the jig models 38, resulting in jig models 38 positionedand oriented relative to point P′ (X_(0-k), Y_(0-k), Z_(0-k)) to allowtheir integration with the bone cut and drill hole data 44 of [block125].

In one embodiment, the procedure for indexing the jig models 38 to thearthroplasty target areas 42 is generally or completely automated, asdisclosed in U.S. patent application Ser. No. 11/959,344 to Park, whichis entitled System and Method for Manufacturing Arthroplasty Jigs, wasfiled Dec. 18, 2007 and is incorporated by reference in its entiretyinto this Detailed Description. For example, a computer program maycreate 3D computer generated surface models 40 of the arthroplastytarget areas 42 of the arthritic models 36. The computer program maythen import the surface models 40 and point P′ (X_(0-k), Y_(0-k),Z_(0-k)) into the jig models 38, resulting in the jig models 38 beingindexed to matingly receive the arthroplasty target areas 42 of thearthritic models 36. The resulting jig models 38 are also positioned andoriented relative to point P′ (X_(0-k), Y_(0-k), Z_(0-k)) to allow theirintegration with the bone cut and drill hole data 44 of [block 125].

In one embodiment, the arthritic models 36 may be 3D volumetric modelsas generated from the closed-loop process discussed in U.S. patentapplication Ser. No. 11/959,344 filed by Park. In other embodiments, thearthritic models 36 may be 3D surface models as generated from theopen-loop process discussed in U.S. patent application Ser. No.11/959,344 filed by Park.

As indicated in FIG. 1E, in one embodiment, the data regarding the jigmodels 38 and surface models 40 relative to point P′ (X_(0-k), Y_(0-k),Z_(0-k)) is packaged or consolidated as the “jig data” 46 [block 145].The “jig data” 46 is then used as discussed below with respect to [block150] in FIG. 1E.

As can be understood from FIG. 1E, the “saw cut and drill hole data” 44is integrated with the “jig data” 46 to result in the “integrated jigdata” 48 [block 150]. As explained above, since the “saw cut and drillhole data” 44, “jig data” 46 and their various ancestors (e.g., models22, 28, 36, 38) are matched to each other for position and orientationrelative to point P and P′, the “saw cut and drill hole data” 44 isproperly positioned and oriented relative to the “jig data” 46 forproper integration into the “jig data” 46. The resulting “integrated jigdata” 48, when provided to the CNC machine 10, results in jigs 2: (1)configured to matingly receive the arthroplasty target areas of thepatient's bones; and (2) having cut slots and drill holes thatfacilitate preparing the arthroplasty target areas in a manner thatallows the arthroplasty joint implants to generally restore thepatient's joint line to its pre-degenerated state or, in other words,the joint's natural alignment.

As can be understood from FIGS. 1A and 1E, the “integrated jig data” 44is transferred from the computer 6 to the CNC machine 10 [block 155].Jig blanks 50 are provided to the CNC machine 10 [block 160], and theCNC machine 10 employs the “integrated jig data” to machine thearthroplasty jigs 2 from the jig blanks 50.

For a discussion of example customized arthroplasty cutting jigs 2capable of being manufactured via the above-discussed process, referenceis made to FIGS. 1F-1I. While, as pointed out above, the above-discussedprocess may be employed to manufacture jigs 2 configured forarthroplasty procedures (e.g., total joint replacement, partial jointreplacement, joint resurfacing, etc.) involving knees, elbows, ankles,wrists, hips, shoulders, vertebra interfaces, etc., the jig examplesdepicted in FIGS. 1F-1I are for total knee replacement (“TKR”) orpartial knee replacement. Thus, FIGS. 1F and 1G are, respectively,bottom and top perspective views of an example customized arthroplastyfemur jig 2A, and FIGS. 1H and 1I are, respectively, bottom and topperspective views of an example customized arthroplasty tibia jig 2B.

As indicated in FIGS. 1F and 1G, a femur arthroplasty jig 2A may includean interior side or portion 100 and an exterior side or portion 102.When the femur cutting jig 2A is used in a TKR or partial kneereplacement procedure, the interior side or portion 100 faces andmatingly receives the arthroplasty target area 42 of the femur lowerend, and the exterior side or portion 102 is on the opposite side of thefemur cutting jig 2A from the interior portion 100.

The interior portion 100 of the femur jig 2A is configured to match thesurface features of the damaged lower end (i.e., the arthroplasty targetarea 42) of the patient's femur 18. Thus, when the target area 42 isreceived in the interior portion 100 of the femur jig 2A during the TKRor partial knee replacement surgery, the surfaces of the target area 42and the interior portion 100 match.

The surface of the interior portion 100 of the femur cutting jig 2A ismachined or otherwise formed into a selected femur jig blank 50A and isbased or defined off of a 3D surface model 40 of a target area 42 of thedamaged lower end or target area 42 of the patient's femur 18.

As indicated in FIGS. 1H and 1I, a tibia arthroplasty jig 2B may includean interior side or portion 104 and an exterior side or portion 106.When the tibia cutting jig 2B is used in a TKR or partial kneereplacement procedure, the interior side or portion 104 faces andmatingly receives the arthroplasty target area 42 of the tibia upperend, and the exterior side or portion 106 is on the opposite side of thetibia cutting jig 2B from the interior portion 104.

The interior portion 104 of the tibia jig 2B is configured to match thesurface features of the damaged upper end (i.e., the arthroplasty targetarea 42) of the patient's tibia 20. Thus, when the target area 42 isreceived in the interior portion 104 of the tibia jig 2B during the TKRor partial knee replacement surgery, the surfaces of the target area 42and the interior portion 104 match.

The surface of the interior portion 104 of the tibia cutting jig 2B ismachined or otherwise formed into a selected tibia jig blank 50B and isbased or defined off of a 3D surface model 40 of a target area 42 of thedamaged upper end or target area 42 of the patient's tibia 20.

b. Overview of Automated Processes for Restoring Damaged Regions of 3DBone Models to Generate 3D Restored Bone Models

As mentioned above with respect to [block 115] of FIG. 1C, the processfor restoring damaged regions of 3D “bone models” 22 to generate 3D“restored bone models” 28 can be automated to be carried out to agreater or lesser extent by a computer. A discussion of various examplesof such an automated process will now concern the remainder of thisDetailed Description, beginning with an overview of various automatedbone restoration processes.

As can be understood from FIG. 1A and [blocks 100-105] of FIG. 1B, apatient 12 has a joint 14 (e.g., a knee, elbow, ankle, wrist, shoulder,hip, vertebra interface, etc.) to be replaced (e.g., partially ortotally) or resurfaced. The patient 12 has the joint 14 scanned in animaging machine 10 (e.g., a CT, MRI, etc. machine) to create a pluralityof 2D scan images 16 of the bones (e.g., femur 18 and tibia 20) formingthe patient's joint 14 (e.g., knee). The process of creating the 2D scanimages or slices 16 may occur as disclosed in Ser. No. 11/946,002, whichwas filed by Park Nov. 27, 2007 and is incorporated by reference in itsentirety into this Detailed Description. Each scan image 16 is a thinslice image of the targeted bone(s) 18, 20. The scan images 16 are sentto the CPU 7, which may employ an open-loop or closed-loop imageanalysis along targeted features 42 of the scan images 16 of the bones18, 20 to generate a contour line for each scan image 16 along theprofile of the targeted features 42. The process of generating contourlines for each scan image 16 may occur as disclosed in Ser. No.11/959,344, which is incorporated by reference in its entirety into thisDetailed Description.

As can be understood from FIG. 1A and [block 110] of FIG. 1C, the CPU 7compiles the scan images 16 and, more specifically, the contour lines togenerate 3D computer surface or volumetric models (“bone models”) 22 ofthe targeted features 42 of the patient's joint bones 18, 20. In thecontext of total knee replacement (“TKR”) or partial knee replacementsurgery, the targeted features 42 may be the lower or knee jointportions of the patient's femur 18 and the upper or knee joint portionsof the patient's tibia 20. More specifically, for the purposes ofgenerating the femur bone models 22, the targeted features 42 mayinclude the condyle portion of the femur and may extend upward toinclude at least a portion of the femur shaft. Similarly, for purposesof generating the tibia bone models 22, the targeted features 42 mayinclude the plateau portion of the tibia and may extend downward toinclude at least a portion of the tibia shaft.

In some embodiments, the “bone models” 22 may be surface models orvolumetric solid models respectively formed via an open-loop orclosed-loop process such that the contour lines are respectively open orclosed loops. Regardless, the bone models 22 are bone-only 3D computergenerated models of the joint bones that are the subject of thearthroplasty procedure. The bone models 22 represent the bones in thedeteriorated condition in which they existed at the time of the medicalimaging of the bones.

To allow for the POP procedure, wherein the saw cut and drill holelocations 30, 32 are determined as discussed with respect to [block 120]of FIG. 1C, the “bone models” 22 and/or the image slices 16 (see [block100] of FIG. 1B) are modified to generate a 3D computer generated modelthat approximates the condition of the patient's bones prior to theirdegeneration. In other words, the resulting 3D computer generated model,which is termed a “restored bone model” 28, approximates the patient'sbones in a non-degenerated or healthy state and can be used to representthe patient's joint in its natural alignment prior to degeneration.

In one embodiment, the bone restoration process employed to generate therestored bone model 28 from the bone model 22 or image slices 16 may beas indicated in the process diagram depicted in FIG. 2. As shown in FIG.2, the damaged and reference sides of a joint bone to undergo anarthroplasty procedure are identified from the 3D computer generated“bone model” [block 200]. The damaged side is the side or portion of thejoint bone that needs to be restored in the bone model 22, and thereference side is the side of the joint bone that is generally undamagedor at least sufficiently free of deterioration that it can serve as areference for restoring the damaged side.

As can be understood from FIG. 2, reference data or information (e.g.,in the form of ellipses, ellipse axes, and/or vectors in the form oflines and/or planes) is then determined from the reference side of thejoint bone [block 205]. The reference information or data is thenapplied to the damaged side of the joint bone [block 215]. For example,in a first embodiment and in the context of a knee joint, a vectorassociated with a femur condyle ellipse of the reference side isdetermined and applied to the damaged side femur condyle and damagedside tibia plateau. In a second embodiment and in the context of a kneejoint, a vector associated with the highest anterior and posteriorpoints of a tibia plateau of the reference side is determined andapplied to the damaged side femur condyle and damaged side tibiaplateau. These vectors are generally parallel with the condyle ellipseand generally parallel with the knee joint line.

As indicated in FIG. 2, each joint contour line associated with a 2Dimage slice of the damaged side of the joint bone is caused to extend tothe reference vector or ellipse [block 220]. This restoration process iscarried out slice-by-slice for the joint contour lines of most, if notall, image slices associated with the damaged side of the joint. The 3D“bone model” is then reconstructed into the 3D “restored bone model”from the restored 2D images slices [block 225].

Once generated from the “bone model” 22, the “restored bone model” 28can then be employed in the POP process discussed with respect to [block120] of FIG. 1C. As discussed with respect to [blocks 125 and 150], “sawcut and drill hole data” resulting from the POP process is indexed into“jig data” 46 to create “integrated jig data” 48. As discussed withrespect to [blocks 155-165] of FIG. 1E, the “integrated jig data” 48 isutilized by a CNC machine 10 to produce customized arthroplasty jigs 2.

The systems 4 and methods disclosed herein allow for the efficientmanufacture of arthroplasty jigs 2 customized for the specific bonefeatures of a patient. Each resulting arthroplasty jig 2 includes aninterior portion dimensioned specific to the surface features of thepatient's bone that are the focus of the arthroplasty. Each jig 2 alsoincludes saw cut slots and drill holes that are indexed relative to theinterior portion of the jig such that saw cuts and drill holesadministered to the patient's bone via the jig will result in cuts andholes that will allow joint implants to restore the patient's joint lineto a pre-degenerated state or at least a close approximation of thepre-degenerated state.

Where the arthroplasty is for TKR or partial knee replacement surgery,the jigs will be a femur jig and/or a tibia jig. The femur jig will havean interior portion custom configured to match the damaged surface ofthe lower or joint end of the patient's femur. The tibia jig will havean interior portion custom configured to match the damaged surface ofthe upper or joint end of the patient's tibia.

The jigs 2 and systems 4 and methods of producing such jigs areillustrated herein in the context of knees and TKR or partial kneereplacement surgery. However, those skilled in the art will readilyunderstand the jigs 2 and system 4 and methods of producing such jigscan be readily adapted for use in the context of other joints and jointreplacement or resurfacing surgeries, e.g., surgeries for elbows,shoulders, hips, etc. Accordingly, the disclosure contained hereinregarding the jigs 2 and systems 4 and methods of producing such jigsshould not be considered as being limited to knees and TKR or partialknee replacement surgery, but should be considered as encompassing alltypes of joint surgeries.

c. Overview of the Mechanics of an Accurate Restored Bone Model

An overview discussion of the mechanics of an accurate restored bonemodel 28 will first be given before discussing any of the bonerestoration procedures disclosed herein. While this overview discussionis given in the context of a knee joint 14 and, more particularly, afemur restored bone model 28A and a tibia restored bone model 28B, itshould be remembered that this discussion is applicable to other joints(e.g., elbows, ankles, wrists, hips, spine, etc.) and should not beconsidered as being limited to knee joints 14, but to include alljoints.

As shown in FIG. 3A, which is a coronal view of a distal or knee jointend of a femur restored bone model 28A, points D₁, D₂ represent the mostdistal tangent contact points of each of the femoral lateral and medialcondyles 300, 302, respectively. In other words, points D₁, D₂ representthe lowest contact points of each of the femoral lateral and medialcondyles 300, 302 when the knee is in zero degree extension. Line D₁D₂can be obtained by extending across the two tangent contact points D₁,D₂. In this femur restored bone model 28A, line D₁D₂ is parallel ornearly parallel to the joint line of the knee when the knee is in zerodegree extension.

The reference line N1 is perpendicular to line D₁D₂ at point D₁ and canbe considered to represent a corresponding 2D image slice 16 taken alongline N1. The reference line N2 is perpendicular to line D₁D₂ at point D₂and can be considered to represent a corresponding 2D image slice 16taken along line N2. The cross-sectional 2D image slices 16 taken alonglines N1, N2 are perpendicular or nearly perpendicular to the tangentline D₁D₂ and joint line.

As shown in FIG. 3B, which is an axial view of a distal or knee jointend of a femur restored bone model 28A, points P₁, P₂ represent the mostposterior tangent contact points of each of the femoral lateral andmedial condyles 300, 302, respectively. In other words, points P₁, P₂represent the lowest contact points of each of the femoral lateral andmedial condyles 300, 302 when the knee is in 90 degree extension. LineP₁P₂ can be obtained by extending across the two tangent contact pointsP₁, P₂. In this femur restored bone model 28A, line P₁P₂ is parallel ornearly parallel to the joint line of the knee when the knee is in 90degree flexion.

The reference line N3 is perpendicular to line P₁P₂ at point P₁ and canbe considered to represent a corresponding 2D image slice 16 taken alongline N3. In some instances, the lines N1, N3 may occupy generally thesame space on the femur restored bone model 28A or lines N1, N3 may beoffset to a greater or lesser extent from each other along the jointline of the knee. The reference line N4 is perpendicular to line P₁P₂ atpoint P₂ and can be considered to represent a corresponding 2D imageslice 16 taken along line N4. In some instances, the lines N2, N4 mayoccupy generally the same space on the femur restored bone model 28A orlines N2, N4 may be offset to a greater or lesser extent from each otheralong the joint line of the knee. The cross-sectional 2D image slices 16taken along lines N3, N4 are perpendicular or nearly perpendicular tothe tangent line P₁P₂ and joint line.

As shown in FIG. 3C, which is a coronal view of a proximal or knee jointend of a tibia restored bone model 28B, points R₁, R₂ represent thelowest tangent contact points of each of the tibial lateral and medialplateaus 304, 306, respectively. In other words, points R₁, R₂ representthe lowest points of contact of the tibia plateau with the femurcondyles when the knee is in zero degree extension. Line R₁R₂ can beobtained by extending across the two tangent contact points R₁, R₂. Inthis tibia restored bone model 28B, line R₁R₂ is parallel or nearlyparallel to the joint line of the knee when the knee is in zero degreeextension. Also, when the knee joint is in zero degree extension, lineR₁R₂ is parallel or nearly parallel to line D₁D₂. When the knee joint isin 90 degree extension, line R₁R₂ is parallel or nearly parallel to lineP₁P₂.

The reference line N1 is perpendicular to line R₁R₂ at point R₁ and canbe considered to represent a corresponding 2D image slice 16 taken alongline N1. The reference line N2 is perpendicular to line R₁R₂ at point R₂and can be considered to represent a corresponding 2D image slice 16taken along line N2. The cross-sectional 2D image slices 16 taken alonglines N1, N2 are perpendicular or nearly perpendicular to the tangentline R₁R₂ and joint line. Because both the femur and tibia restored bonemodels 28A, 28B represent the knee joint 14 prior to degeneration ordamage, lines N1, N2 of the femur restored model 28A in FIG. 1A alignwith and may be the same as lines N1, N2 of the tibia restored bonemodel 28B when the knee joint is in zero degree extension. Thus, pointsD₁, D₂ align with points R₁, R₂ when the knee joint is in zero degreeextension.

FIG. 3D represents the femur and tibia restored bone models 28A, 28B inthe views depicted in FIGS. 3A and 3C positioned together to form a kneejoint 14. FIG. 3D shows the varus/valgus alignment of the femur andtibia restored bone models 28A, 28B intended to restore the patient'sknee joint 14 back to its pre-OA or pre-degenerated state, wherein theknee joint 14 is shown in zero degree extension and in its naturalalignment (e.g., neutral, varus or valgus) as the knee joint existedprior to degenerating. The respective locations of the lateralcollateral ligament (“LCL”) 308 and medial collateral ligament (“MCL”)310 are indicated in FIG. 3D by broken lines and serve as stabilizersfor the side-to-side stability of the knee joint 14.

As can be understood from FIGS. 3A, 3C and 3D, when the knee joint 14 isin zero degree extension, lines N1, N2 are parallel or nearly parallelto the LCL 308 and MCL 310. Gap t1 represents the distance between thetangent contact point D₁ of the femoral lateral condyle 300 and thetangent contact point R₁ of the tibia lateral plateau 304. Gap t2represents the distance between the tangent contact point D₂ of thefemoral medial condyle 302 and the tangent contact point R₂ of themedial tibia plateau 306. For a properly restored knee joint 14, asdepicted in FIG. 3D, in one embodiment, with respect to varus/valgusrotation and alignment, t1 is substantially equal to t2 such that thedifference between t1 and t2 is less than one millimeter (e.g.,[t1−t2]<<1 mm). Accordingly, line D₁D₂ is parallel or nearly parallel tothe joint line and line R₁R₂.

FIG. 3E represents the femur and tibia restored bone models 28A, 28B inthe views depicted in FIGS. 3B and 3C positioned together to form a kneejoint 14. FIG. 3E shows the varus/valgus alignment of the femur andtibia restored bone models 28A, 28B intended to restore the patient'sknee joint 14 back to its pre-OA or pre-degenerated state, wherein theknee joint 14 is shown in 90 degree flexion and in its natural alignment(e.g., neutral, varus or valgus) as the knee joint existed prior todegenerating. The respective locations of the lateral collateralligament (“LCL”) 308 and medial collateral ligament (“MCL”) 310 areindicated in FIG. 3E by broken lines and serve as stabilizers for theside-to-side stability of the knee joint 14.

As can be understood from FIGS. 3B, 3C and 3E, when the knee joint 14 isin 90 degree flexion, lines N3, N4 are parallel or nearly parallel tothe LCL 308 and MCL 310. Gap h1 represents the distance between thetangent contact point P₁ of the femoral lateral condyle 300 and thetangent contact point R₁ of the tibia lateral plateau 304. Gap h2represents the distance between the tangent contact point P₂ of thefemoral medial condyle 302 and the tangent contact point R₂ of themedial tibia plateau 306. For a properly restored knee joint 14, asdepicted in FIG. 3E, in one embodiment, with respect to varus/valgusrotation and alignment, h1 is substantially equal to h2 such that thedifference between h1 and h2 is less than one millimeter (e.g.,[h1−h2]<<1 mm). Accordingly, line P₁P₂ is parallel or nearly parallel tothe joint line and line R₁R₂.

FIG. 3F is a sagittal view of the femoral medial condyle ellipse 300and, more specifically, the N1 slice of the femoral medial condyleellipse 300 as taken along line N1 in FIG. 3A. The contour line N₁ inFIG. 3F represents the N1 image slice of the femoral medial condyle 300.The N1 image slice may be generated via such imaging methods as MRI, CT,etc. An ellipse contour 305 of the medial condyle 300 can be generatedalong contour line N₁. The ellipse 305 corresponds with most of thecontour line N₁ for the N1 image slice, including the posterior anddistal regions of the contour line N₁ and portions of the anteriorregion of the contour line N₁. As can be understood from FIG. 3F anddiscussed in greater detail below, the ellipse 305 provides a relativelyclose approximation of the contour line N₁ in a region of interest orregion of contact A_(i) that corresponds to an region of the femoralmedial condyle surface that contacts and displaces against the tibiamedial plateau.

As can be understood from FIGS. 3A, 3B and 3F, the ellipse 305 can beused to determine the distal extremity of the femoral medial condyle300, wherein the distal extremity is the most distal tangent contactpoint D₁ of the femoral medial condyle 300 of the N1 slice. Similarly,the ellipse 305 can be used to determine the posterior extremity of thefemoral medial condyle 300, wherein the posterior extremity is the mostposterior tangent contact point P₁′ of the femoral medial condyle 300 ofthe N1 slice. The ellipse origin point O₁, the ellipse major axisP₁′PP₁′ and ellipse minor axis D₁DD₁ can be obtained based on theelliptical shape of the N1 slice of the medial condyle 300 inconjunction with well-known mathematical calculations for determiningthe characteristics of an ellipse.

As can be understood from FIG. 3F and as mentioned above, the region ofcontact A_(i) represents or corresponds to the overlapping surfaceregion between the medial tibia plateau 304 and the femoral medialcondyle 300 along the N1 image slice. The region of contact A_(i) forthe N1 image slice is approximately 120° of the ellipse 305 of the N1image slice from just proximal the most posterior tangent contact pointPC to just anterior the most distal tangent contact point D₁.

FIG. 3G is a sagittal view of the femoral lateral condyle ellipse 302and, more specifically, the N2 slice of the femoral lateral condyleellipse 302 as taken along line N2 in FIG. 3A. The contour line N₂ inFIG. 3G represents the N2 image slice of the femoral lateral condyle302. The N2 image slice may be generated via such imaging methods asMRI, CT, etc. An ellipse contour 305 of the lateral condyle 302 can begenerated along contour line N₂. The ellipse 305 corresponds with mostof the contour line N₂ for the N2 image slice, including the posteriorand distal regions of the contour line N₂ and portions of the anteriorregion of the contour line N₂. As can be understood from FIG. 3G anddiscussed in greater detail below, the ellipse 305 provides a relativelyclose approximation of the contour line N₂ in a region of interest orregion of contact A_(i) that corresponds to an region of the femorallateral condyle surface that contacts and displaces against the tibialateral plateau.

As can be understood from FIGS. 3A, 3B and 3G, the ellipse 305 can beused to determine the distal extremity of the femoral lateral condyle302, wherein the distal extremity is the most distal tangent contactpoint D₂ of the femoral lateral condyle 302 of the N2 slice. Similarly,the ellipse 305 can be used to determine the posterior extremity of thefemoral lateral condyle 302, wherein the posterior extremity is the mostposterior tangent contact point P₂′ of the femoral lateral condyle 302of the N2 slice. The ellipse origin point O₂, the ellipse major axisP₂′PP₂′ and ellipse minor axis D₂DD₂ can be obtained based on theelliptical shape of the N2 slice of the lateral condyle 302 inconjunction with well-known mathematical calculations for determiningthe characteristics of an ellipse.

As can be understood from FIG. 3G and as mentioned above, the region ofcontact A_(i) represents or corresponds to the overlapping surfaceregion between the lateral tibia plateau 306 and the femoral lateralcondyle 302 along the N2 image slice. The region of contact A_(i) forthe N2 image slice is approximately 120° of the ellipse 305 of the N2image slice from just proximal the most posterior tangent contact pointP₂′ to just anterior the most distal tangent contact point D₂.

FIG. 3H is a sagittal view of the femoral medial condyle ellipse 300and, more specifically, the N3 slice of the femoral medial condyleellipse 300 as taken along line N3 in FIG. 3B. The contour line N₃ inFIG. 3H represents the N3 image slice of the femoral medial condyle 300.The N3 image slice may be generated via such imaging methods as MRI, CT,etc. An ellipse contour 305 of the medial condyle 300 can be generatedalong contour line N₃. The ellipse 305 corresponds with most of thecontour line N₃ for the N3 image slice, including the posterior anddistal regions of the contour line N₃ and portions of the anteriorregion of the contour line N₃. As can be understood from FIG. 3H anddiscussed in greater detail below, the ellipse 305 provides a relativelyclose approximation of the contour line N₃ in a region of interest orregion of contact A_(i) that corresponds to an region of the femoralmedial condyle surface that contacts and displaces against the tibiamedial plateau.

As can be understood from FIGS. 3A, 3B and 3H, the ellipse 305 can beused to determine the distal extremity of the femoral medial condyle300, wherein the distal extremity is the most distal tangent contactpoint D₁′ of the femoral medial condyle 300 of the N3 slice. Similarly,the ellipse 305 can be used to determine the posterior extremity of thefemoral medial condyle 300, wherein the posterior extremity is the mostposterior tangent contact point P₁ of the femoral medial condyle 300 ofthe N3 slice. The ellipse origin point O₃, the ellipse major axis P₁PP₁and ellipse minor axis D₁′DD₁′ can be obtained based on the ellipticalshape of the N3 slice of the medial condyle 300 in conjunction withwell-known mathematical calculations for determining the characteristicsof an ellipse.

As can be understood from FIG. 3H and as mentioned above, the region ofcontact A_(i) represents or corresponds to the overlapping surfaceregion between the medial tibia plateau 304 and the femoral medialcondyle 300 along the N3 image slice. The region of contact A_(i) forthe N3 image slice is approximately 120° of the ellipse 305 of the N3image slice from just proximal the most posterior tangent contact pointP₁ to just anterior the most distal tangent contact point D₁′.

FIG. 3I is a sagittal view of the femoral lateral condyle ellipse 302and, more specifically, the N4 slice of the femoral lateral condyleellipse 302 as taken along line N4 in FIG. 3B. The contour line N₄ inFIG. 3I represents the N4 image slice of the femoral lateral condyle302. The N4 image slice may be generated via such imaging methods asMRI, CT, etc. An ellipse contour 305 of the lateral condyle 302 can begenerated along contour line N₄. The ellipse 305 corresponds with mostof the contour line N₄ for the N4 image slice, including the posteriorand distal regions of the contour line N₄ and portions of the anteriorregion of the contour line N₄. As can be understood from FIG. 3G anddiscussed in greater detail below, the ellipse 305 provides a relativelyclose approximation of the contour line N₄ in a region of interest orregion of contact A_(i) that corresponds to an region of the femorallateral condyle surface that contacts and displaces against the tibialateral plateau.

As can be understood from FIGS. 3A, 3B and 3I, the ellipse 305 can beused to determine the distal extremity of the femoral lateral condyle302, wherein the distal extremity is the most distal tangent contactpoint D₂′ of the femoral lateral condyle 302 of the N4 slice. Similarly,the ellipse 305 can be used to determine the posterior extremity of thefemoral lateral condyle 302, wherein the posterior extremity is the mostposterior tangent contact point P₂ of the femoral lateral condyle 302 ofthe N4 slice. The ellipse origin point O₄, the ellipse major axis P₂PP₂and ellipse minor axis D₂′DD₂′ can be obtained based on the ellipticalshape of the N4 slice of the lateral condyle 302 in conjunction withwell-known mathematical calculations for determining the characteristicsof an ellipse.

As can be understood from FIG. 3I and as mentioned above, the region ofcontact A_(i) represents or corresponds to the overlapping surfaceregion between the lateral tibia plateau 306 and the femoral lateralcondyle 302 along the N4 image slice. The region of contact A_(i) forthe N4 image slice is approximately 120° of the ellipse 305 of the N4image slice from just proximal the most posterior tangent contact pointP₂ to just anterior the most distal tangent contact point D₂′.

While the preceding discussion is given in the context of image slicesN1, N2, N3 and N4, of course similar elliptical contour lines, ellipseaxes, tangent contact points and contact regions may be determined forthe other image slices generated during the imaging of the patient'sjoint and which are parallel to image slices N1, N2, N3 and N4.

d. Employing Vectors from a Reference Side of a Joint to a Damaged Sideof a Joint and Extending the Contour Lines of the Damaged Side to Meetthe Vectors to Restore the Damaged Side

A discussion of methods for determining reference vectors from areference side of a joint bone for use in restoring a damaged side ofthe joint bone is first given, followed by specific examples of therestoration process in the context of MRI images. While this overviewdiscussion is given in the context of a knee joint 14 and, moreparticularly, femur and tibia bone models 22A, 22B being converted imageslice by slice into femur and tibia restored bone models 28A, 28B, itshould be remembered that this discussion is applicable to other joints(e.g., elbows, ankles, wrists, hips, spine, etc.) and should not beconsidered as being limited to knee joints 14, but to include alljoints. Also, while the image slices are discussed in the context of MRIimage slices, it should be remembered that this discussion is applicableto all types of medical imaging, including CT scanning.

For a discussion of the motion mechanism of the knee and, morespecifically, the motion vectors associated with the motion mechanism ofthe knee, reference is made to FIGS. 4A and 4B. FIG. 4A is a sagittalview of the lateral tibia plateau 304 with the lateral femur condyleellipse 305 of the N1 slice of FIG. 3F superimposed thereon. FIG. 4B isa sagittal view of the medial tibia plateau 306 with the lateral femurcondyle ellipse 305 of the N2 slice of FIG. 3G superimposed thereon.

The motion mechanism for a human knee joint operates as follows. Thefemoral condyles glide on the corresponding tibia plateaus as the kneemoves, and in a walking theme, as a person's leg swings forward, thefemoral condyles and the corresponding tibia plateaus are not under thecompressive load of the body. Thus, the knee joint movement is a slidingmotion of the tibia plateaus on the femoral condyles coupled with arolling of the tibia plateaus on the femoral condyles in the samedirection. The motion mechanism of the human knee as the femur condylesand tibia plateaus move relative to each other between zero degreeflexion and 90 degree flexion has associated motion vectors. Asdiscussed below, the geometrical features of the femur condyles andtibia plateaus can be analyzed to determine vectors U₁, U₂, V₁, V₂, V₃,V₄ that are associated with image slices N1, N2, N3 and N4. Thesevectors U₁, U₂, V₁, V₂, V₃, V₄ correspond to the motion vectors of thefemur condyles and tibia plateaus moving relative to each other. Thedetermined vectors U₁, U₂, V₁, V₂, V₃, V₄ associated with a healthy sideof a joint 14 can be applied to a damaged side of a joint 14 to restorethe bone model 22 to create a restored bone model 28.

In some embodiments of the bone restoration process disclosed herein andas just stated, the knee joint motion mechanism may be utilized todetermine the vector references for the restoration of bone models 22 torestored bone models 28. As can be understood from a comparison of FIGS.3F and 3G to FIGS. 4A and 4B, the U₁ and U₂ vectors respectivelycorrespond to the major axes P₁′PP₁′ and P₂′PP₂′ of the ellipses 305 ofthe N1 and N2 slices. Since the major axes P₁′PP₁′ and P₂′PP₂′ exist inthe N1 and N2 slices, which are planes generally perpendicular to thejoint line, the U₁ and U₂ vectors may be considered to represent bothvector lines and vector planes that are perpendicular to the joint line.

The U₁ and U₂ vectors are based on the joint line reference between thefemur and the tibia from the zero degree flexion (full extension) to 90degree flexion. The U₁ and U₂ vectors represent the momentary slidingmovement force from zero degree flexion of the knee to any degree offlexion up to 90 degree flexion. As can be understood from FIGS. 4A and4B, the U₁ and U₂ vectors, which are the vectors of the femoralcondyles, are generally parallel to and project in the same direction asthe V₁ and V₂ vectors of the tibia plateaus 321, 322. The vector planesassociated with these vectors U₁, U₂, V₁, V₂ are presumed to be parallelor nearly parallel to the joint line of the knee joint 14 represented byrestored bone model 28A, 28B such as those depicted in FIGS. 3D and 3E.

As shown in FIGS. 4A and 4B, the distal portion of the ellipses 305extend along and generally correspond with the curved surfaces 321, 322of the tibia plateaus. The curved portions 321, 322 of the tibiaplateaus that generally correspond with the distal portions of theellipses 305 represent the tibia contact regions A_(k), which are theregions that contact and displace along the femur condyles andcorrespond with the condyle contact regions A_(i) discussed with respectto FIGS. 3F-3I.

For a discussion of motion vectors associated with the tibia plateaus,reference is made to FIGS. 4C-4E. FIG. 4C is a top view of the tibiaplateaus 304, 306 of a restored tibia bone model 28B. FIG. 4D is asagittal cross section through a lateral tibia plateau 304 of therestored bone model 28B of FIG. 4C and corresponding to the N3 imageslice of FIG. of FIG. 3B. FIG. 4E is a sagittal cross section through amedial tibia plateau 306 of the restored bone model 28B of FIG. 4C andcorresponding to the N4 image slice of FIG. of FIG. 3B.

As shown in FIGS. 4C-4E, each tibia plateau 304, 306 includes a curvedrecessed condyle contacting surface 321, 322 that is generally concaveextending anterior/posterior and medial/lateral. Each curved recessedsurface 321, 322 is generally oval in shape and includes an anteriorcurved edge 323, 324 and a posterior curved edge 325, 326 thatrespectively generally define the anterior and posterior boundaries ofthe condyle contacting surfaces 321, 322 of the tibia plateaus 304, 306.Depending on the patient, the medial tibia plateau 306 may have curvededges 324, 326 that are slightly more defined than the curved edges 323,325 of the lateral tibia plateau 304.

Anterior tangent lines T_(Q3), T_(Q4) can be extended tangentially tothe most anterior location on each anterior curved edge 323, 324 toidentify the most anterior points Q3, Q4 of the anterior curved edges323, 324. Posterior tangent lines T_(Q3′), T_(Q4′) can be extendedtangentially to the most posterior location on each posterior curvededge 325, 326 to identify the most posterior points Q3′, Q4′ of theposterior curved edges 325, 326. Such anterior and posterior points maycorrespond to the highest points of the anterior and posterior portionsof the respective tibia plateaus.

Vector line V3 extends through anterior and posterior points Q3, Q3′,and vector line V4 extends through anterior and posterior points Q4,Q4′. Each vector line V3, V4 may align with the lowest point of theanterior-posterior extending groove/valley that is the ellipticalrecessed tibia plateau surface 321, 322. The lowest point of theanterior-posterior extending groove/valley of the elliptical recessedtibia plateau surface 321, 322 may be determined via simple ellipsoidcalculus. Each vector V3, V4 will be generally parallel to theanterior-posterior extending valleys of its respective ellipticalrecessed tibia plateau surface 321, 322 and will be generallyperpendicular to it respective tangent lines T_(Q3), T_(Q4), T_(Q3′),T_(Q4′). The anterior-posterior extending valleys of the ellipticalrecessed tibia plateau surfaces 321, 322 and the vectors V3, V4 alignedtherewith may be generally parallel with and even exist within the N3and N4 image slices depicted in FIG. 3B.

As can be understood from FIGS. 4A-4E, the V₃ and V₄ vectors, which arethe vectors of the tibia plateaus, are generally parallel to and projectin the same direction as the other tibia plateau vectors V₁ and V₂ and,as a result, the femur condyle vectors U₁, U₂. The vector planesassociated with these vectors U₁, U₂, V₁, V₂, V₃ and V₄ are presumed tobe parallel or nearly parallel to the joint line of the knee joint 14represented by restored bone models 28A, 28B such as those depicted inFIGS. 3D and 3E.

As indicated in FIGS. 4A-4C, tibia plateau vectors V₁ and V₂ in the N1and N2 image slices can be obtained by superimposing the femoral condyleellipses 305 of the N1 and N2 image slices onto their respective tibiaplateaus. The ellipses 305 correspond to the elliptical tibia plateausurfaces 321, 322 along the condyle contact regions A_(k) of the tibiaplateaus 304, 306. The anterior and posterior edges 323, 324, 325, 326of the elliptical tibia plateau surfaces 321, 322 can be determined atthe locations where the ellipses 305 cease contact with the plateausurfaces 321. 322. These edges 323, 324, 325, 326 are marked as anteriorand posterior edge points Q1, Q1′, Q2, Q2′ in respective image slices N1and N2. Vector lines V1 and V2 are defined by being extended throughtheir respective edge points Q1, Q1′, Q2, Q2′.

As can be understood from FIG. 4C, image slices N1, N2, N3 and N4 andtheir respective vectors V₁, V₂, V₃ and V₄ may be medially-laterallyspaced apart a greater or lesser extent, depending on the patient. Withsome patients, the N1 and N3 image slices and/or the N2 and N4 imageslices may generally medially-laterally align.

While the preceding discussion is given with respect to vectors U₁, U₂,V₁, V₂, V₃ and V₄, contact regions A_(i), A_(k), and anterior andposterior edge points Q1, Q1′, Q2, Q2′, Q3, Q3′, Q4, Q4′ associated withimage slices N1, N2, N3 and N4, similar vectors, contact regions, andanterior and posterior edge points can be determined for the other imageslices 16 used to generate the 3D computer generated bone models 22 (see[block 100]-[block 110] of FIGS. 1A-1C).

As illustrated via the following examples given with respect to MRIslices, vectors similar to the U₁, U₂, V₁, V₂, V₃, V₄ vectors of FIGS.4A-4E can be employed in restoring image slice-by-image slice the bonemodels 22A, 22B into restored bone models 28A, 28B. For example, a bonemodel 22 includes a femur bone model 22A and a tibia bone model 22B. Thebone models 22A, 22B are 3D bone-only computer generated models compiledvia any of the above-mentioned 3D computer programs from a number ofimage slices 16, as discussed with respect to [blocks 100]-[block 110]of FIGS. 1A-1C. Depending on the circumstances and generally speaking,either the medial side of the bone models will be generally undamagedand the lateral side of the bone models will be damaged, or vice versa.

For example, as indicated in FIG. 4F, which is a posterior-lateralperspective view of femur and tibia bone models 22A, 22B forming a kneejoint 14, the medial sides 302, 306 of the bone models 22A, 22B are in agenerally non-deteriorated condition and the lateral sides 300, 304 ofthe bone models 22A, 22B are in a generally deteriorated or damagedcondition. The lateral sides 300, 304 of the femur and tibia bone models22A, 22B depict the damaged bone attrition on the lateral tibia plateauand lateral femoral condyle. The lateral sides 300, 304 illustrate thetypical results of OA, specifically joint deterioration in the region ofarrow L_(S) between the femoral lateral condyle 300 and the lateraltibia plateau 304, including the narrowing of the lateral joint space330 as compared to medial joint space 332. As the medial sides 302, 306of the bone models 22A, 22B are generally undamaged, these sides 302,306 will be identified as the reference sides of the 3D bone models 22A,22B (see [block 200] of FIG. 2). Also, as the lateral sides 300, 304 ofthe bone models 22A, 22B are damaged, these sides 300, 304 will beidentified as the damaged sides of the 3D bone models 22A, 22B (see[block 200] of FIG. 2) and targeted for restoration, wherein the imagesslices 16 associated with the damaged sides 300, 304 of the bone models22A, 22B are restored slice-by-slice.

Reference vectors like the U₁, U₂, V₁, V₂, V₃, V₄ vectors may bedetermined from the reference side of the bone models 22A, 22B (see[block 205] of FIG. 2). Thus, as can be understood from FIGS. 4B and 4F,since the medial sides 302, 306 are the reference sides 302, 306, thereference vectors U₂, V₂ V₄ may be applied to the damaged sides 300, 304to restore the damaged sides 300, 304 2D image slice by 2D image slice(see [block 215]-[block 220] of FIG. 2). The restored image slices arethen recompiled into a 3D computer generated model, the result being the3D computer generated restored bone models 28A, 28B (see [block 225] ofFIG. 2).

As shown in FIG. 4G, which is a posterior-lateral perspective view offemur and tibia restored bone models 28A, 28B forming a knee joint 14,the lateral sides 300, 304 of the restored bone models 28A, 28B havebeen restored such that the lateral and medial joint spaces 330, 332 aregenerally equal. In other words, the distance t1 between the lateralfemur condyle and lateral tibia plateau is generally equal to thedistance t2 between the medial femur condyle and the medial tibiaplateau.

The preceding discussion has occurred in the context of the medial sides302, 306 being the reference sides and the lateral sides 300, 304 beingthe damaged sides; the reference vectors U₂, V₂ and V₄ of the medialsides 302, 306 being applied to the damaged sides 300, 304 in theprocess of restoring the damaged sides 300, 304. Of course, as statedabove, the same process could occur in a reversed context, wherein thelateral sides 300, 304 are generally undamaged and are identified as thereference sides, and the medial sides 302, 306 are damaged andidentified as the damaged sides. The reference vectors U₁, V₁ and V₃ ofthe lateral sides 300, 304 can then be applied to the damaged sides 302,306 in the process of restoring the damaged sides 302, 306.

Multiple approaches are disclosed herein for identifying referencevectors and applying the reference vectors to a damaged side for therestoration thereof. For example, as can be understood from FIGS. 4B and4F, where the medial sides 302, 306 are the undamaged reference sides302, 304 and the lateral sides 300, 304 the damaged sides 300, 304, inone embodiment, the ellipses and vectors associated with the referenceside femur condyle 302 (e.g., the ellipse 305 of the N2 slice and thevector U₂) can be applied to the damaged side femur condyle 300 anddamaged side tibia plateau 304 to restore the damaged condyle 300 anddamaged plateau 304. Alternatively or additionally, the ellipses andvectors associated with the reference side femur condyle 302 as appliedto the reference side tibia plateau 306 (e.g., the ellipse 305 of the N2slice and the vector V₂) can be applied to the damaged side femurcondyle 300 and damaged side tibia plateau 304 to restore the damagedcondyle 300 and damaged plateau 304. In another embodiment, as can beunderstood from FIGS. 4C, 4E and 4F, the vectors associated with thereference side tibia plateau 306 (e.g., the vector V₄) can be applied tothe damaged side femur condyle 300 and damaged side tibia plateau 304 torestore the damaged condyle 300 and damaged plateau 304. Of course, ifthe conditions of the sides 300, 302, 304, 306 were reversed in FIG. 4F,the identification of the reference sides, the damaged sides, thereference vectors and the application thereof would be reversed fromexamples given in this paragraph.

1. Employing Vectors from a Femur Condyle of a Reference Side of a KneeJoint to Restore the Femur Condyle and Tibia Plateau of the Damaged Side

For a discussion of a first scenario, wherein the medial sides 302, 306are the damaged sides and the lateral sides 300, 304 are the referencesides, reference is made to FIGS. 5A-5B. FIG. 5A is a coronal view of afemur bone model 22A, and FIG. 5B is a coronal view of a tibia bonemodel 22B.

As shown in FIG. 5A, the medial femur condyle 302 is deteriorated inregion 400 such that the most distal point of the medial condyle 302fails to intersect point D₂ on line D₁D₂, which will be corrected oncethe femur bone model 22A is properly restored to a restored femur bonemodel 28A such as that depicted in FIG. 3A. As illustrated in FIG. 5B,the medial tibia plateau 306 is deteriorated in region 401 such that thelowest point of the medial plateau 306 fails to intersect point R₂ online R₁R₂, which will be corrected once the tibia bone model 22B isproperly restored to a restored tibia bone model 28B such as thatdepicted in FIG. 3C. Because the medial condyle 302 and medial plateau306 of the bone models 22A, 22B are deteriorated, they will beidentified as the damaged sides and targeted for restoration ([block200] of FIG. 2).

As illustrated in FIG. 5A, the lateral condyle 300 and lateral plateau304 of the bone models 22A, 22B are in a generally non-deterioratedstate, the most distal point D₁ of the lateral condyle 300 intersectingline D₁D₂, and the lowest point R₁ of the lateral plateau 304intersecting line R₁R₂. Because the lateral condyle 300 and lateralplateau 304 of the bone models 22A, 22B are generally in anon-deteriorated state, they will be identified as the reference sidesand the source of information used to restore the damaged sides 302, 306([block 200] of FIG. 2).

As can be understood from FIGS. 3F, 4A and 5A, for most if not all ofthe image slices 16 of the lateral condyle 300, image slice informationor data such as ellipses and vectors can be determined. For example, anellipse 305 and vector U₁ can be determined for the N1 slice ([block205] of FIG. 2). The data or information associated with one or more ofthe various slices 16 of the lateral condyle 300 is applied to orsuperimposed on one or more image slices 16 of the medial condyle 302([block 215] of FIG. 2). For example, as shown in FIG. 5C1, which is anN2 image slice of the medial condyle 302 as taken along the N2 line inFIG. 5A, data or information pertaining to the N1 slice is applied to orsuperimposed on the N2 image slice to determine the extent ofrestoration needed in deteriorated region 400. For example, the data orinformation pertaining to the N1 slice may be in the form of the N1slice's ellipse 305-N1, vector U₁, ellipse axes P₁′PP₁′, D₁DD₁, etc. Theellipse 305-N1 will inherently contain its major and minor axisinformation, and the vector U₁ of the N1 slice will correspond to themajor axis of the 305-N1 ellipse and motion vector of the femur condylesrelative to the tibia plateaus. The major axis of the 305-N1 and thevector U₁ of the N1 slice are generally parallel to the joint lineplane.

In a first embodiment, the N1 slice information may be applied only tothe contour line of the N2 slice or another specific slice. In otherwords, information of a specific reference slice may be applied to acontour line of a single specific damaged slice with which the specificreference slice is coordinated with via manual selection or an algorithmfor automatic selection. For example, in one embodiment, the N1 sliceinformation may be manually or automatically coordinated to be appliedonly to the N2 slice contour line, and the N3 slice information may bemanually or automatically coordinated to be applied only to the N4 slicecontour line. Other reference side slice information may be similarlycoordinated with and applied to other damaged side slice contours in asimilar fashion. Coordination between a specific reference slice and aspecific damaged slice may be according to various criteria, forexample, similarity of the function and/or shape of the bone regionspertaining to the specific reference slice and specific damaged sliceand/or similarity of accuracy and dependability for the specificreference slice and specific damaged slice.

In a second embodiment, the N1 slice information or the sliceinformation of another specific slice may be the only image slice usedas a reference slice for the contour lines of most, if not all, of thedamaged slices. In other words, the N1 image slice information may bethe only reference side information used (i.e., to the exclusion of, forexample, the N3 image slice information) in the restoration of thecontour lines of most, if not each, damaged side image slice (i.e., theN1 image slice information is applied to the contour lines of the N2 andN4 image slices and the N3 image slice information is not used). In suchan embodiment, the appropriate single reference image slice may beidentified via manual identification or automatic identification via,for example, an algorithm. The identification may be according tocertain criteria, such as, for example, which reference image slice ismost likely to contain the most accurate and dependable referenceinformation.

While the second embodiment is discussed with respect to informationfrom a single reference image being applied to the contour lines ofmost, if not all, damaged side image slices, in other embodiments, thereference information applied to the contour lines of the damaged imageslices may be from more than one image slice. For example, informationfrom two or more reference image slices (e.g., N1 image slice and N3image slice) are applied individually to the contour lines of thevarious damage image slices. In one embodiment, the information from thetwo or more reference image slices may be combined (e.g., averaged) andthe combined information then applied to the contour lines of individualdamaged image slices.

In some embodiments, the reference side data or information may includea distal tangent line DTL and a posterior tangent line PTL. The distaltangent line DTL may tangentially intersect the extreme distal point ofthe reference image slice and be parallel to the major axis of thereference image slice ellipse. For example, with respect to the N1 imageslice serving as a reference side image slice, the distal tangent lineDTL may tangentially intersect the extreme distal point D₁ of thereference N1 image slice and be parallel to the major axis P₁′PP₁′ ofthe reference N1 image slice ellipse 305-N1.

The posterior tangent line PTL may tangentially intersect the extremeposterior point of the reference image slice and be parallel to themajor axis of the reference image slice ellipse. For example, withrespect to the N1 image slice serving as a reference side image slice,the posterior tangent line PTL may tangentially intersect the extremeposterior point P₁ of the reference N1 image slice and be parallel tothe minor axis D₁DD₁ of the reference N1 image slice ellipse 305-N1.

As can be understood from FIGS. 3F-3I, most, if not all, femur condyleimage slices N1, N2, N3, N4 will have an origin O₁, O₂, O₃, O₄associated with the ellipse 305 used to describe or define the condylesurfaces of each slice N1, N2, N3, N4. When these image slices arecombined together to form the 3D computer generated bone models 22, thevarious origins O₁, O₂, O₃, O₄ will generally align to form a femur axisAO_(F) extending medial-lateral through the femur bone model 22A asdepicted in FIG. 5A. This axis AO_(F) can be used to properly orientreference side data (e.g., the ellipse 305-N1 and vector U₁ of the N1slice in the current example) when being superimposed onto a damagedside image slice (e.g., the N2 image slice in the current example). Theorientation of the data or information of the reference side does notchange as the data or information is being superimposed or otherwiseapplied to the damaged side image slice. For example, the orientation ofthe ellipse 305-N1 and vector U₁ of the N1 slice is maintained or heldconstant during the superimposing of such reference information onto theN2 slice such that the reference information does not change withrespect to orientation or spatial ratios relative to the femur axisAO_(F) when being superimposed on or otherwise applied to the N2 slice.Thus, as described in greater detail below, since the reference sideinformation is indexed to the damaged side image slice via the axisAO_(F) and the orientation of the reference side information does notchange in the process of being applied to the damaged side image slice,the reference side information can simply be adjusted with respect tosize, if needed and as described below with reference to FIGS. 5C2 and5C3, to assist in the restoration of the damaged side image slice.

While the reference side information may be positionally indexedrelative to the damaged side image slices via the femur reference axisAO_(F) when being applied to the damaged side image slices, other axesmay be used for indexing besides an AO axis that runs through or nearthe origins of the respective image slice ellipses. For example, areference axis similar to the femur reference axis AO_(F) and runningmedial-lateral may pass through other portions of the femur bone model22A or outside the femur bone model 22A and may be used to positionallyindex the reference side information to the respective damaged sideimage slices.

The contour line N₂ of the N2 image slice, as with any contour line ofany femur or tibia image slice, may be generated via an open or closedloop computer analysis of the cortical bone of the medial condyle 302 inthe N2 image slice, thereby outlining the cortical bone with an open orclosed loop contour line N₂. Where the contour lines are closed loop,the resulting 3D models 22, 28 will be 3D volumetric models. Where thecontour lines are open loop, the resulting 3D models 22, 28 will be 3Dsurface models.

While in some cases the reference information from a reference imageslice may be substantially similar in characteristics (e.g., size and/orratios) to the damaged image slice contour line to be simply applied tothe contour line, in many cases, the reference information may need tobe adjusted with respect to size and/or ratio prior to using thereference information to restore the damaged side contour line asdiscussed herein with respect to FIGS. 5C1 and 5D. For example, asindicated in FIG. 5C2, which is the same view as FIG. 5C1, exceptillustrating the reference information is too small relative to thedamaged side contour line, the reference information should be increasedprior to being used to restore the damaged side contour line. In otherwords, the N1 information (e.g., the N1 ellipse, vector and tangentlines PTL, DTL), when applied to the contour line of the N2 image slicebased on the AO axis discussed above, is too small for at least some ofthe reference information to match up with at least some of the damagedcontour line at the most distal or posterior positions. Accordingly, ascan be understood from a comparison of FIGS. 5C1 and 5C2, the N1information may be increased in size as needed, but maintaining itsratios (e.g., the ratio of the major/minor ellipse axes to each otherand the ratios of the offsets of the PTL, DTL from the origin or AOaxis), until the N1 information begins to match a boundary of thecontour line of the N2 image slice. For example, as depicted in FIG.5C2, the N1 ellipse is superimposed over the N2 image slice andpositionally coordinated with the N2 image slice via the AO axis. The N1ellipse is smaller than needed to match the contour line of the N2 imageslice and is expanded in size until a portion (e.g., the PTL and P₁′ ofthe N1 ellipse) matches a portion (e.g., the most posterior point) ofthe elliptical contour line of the N2 image slice. A similar process canalso be applied to the PTL and DTL, maintaining the ratio of the PTL andDTL relative to the AO axis. As illustrated in FIG. 5C1, the N1information now corresponds to at least a portion of the damaged imageside contour line and can now be used to restore the contour line asdiscussed below with respect to FIG. 5D.

as indicated in FIG. 5C3, which is the same view as FIG. 5C1, exceptillustrating the reference information is too large relative to thedamaged side contour line, the reference information should be decreasedprior to being used to restore the damaged side contour line. In otherwords, the N1 information (e.g., the N1 ellipse, vector and tangentlines PTL, DTL), when applied to the contour line of the N2 image slicebased on the AO axis discussed above, is too large for at least some ofthe reference information to match up with at least some of the damagedcontour line at the most distal or posterior positions. Accordingly, ascan be understood from a comparison of FIGS. 5C1 and 5C3, the N1information may be decreased in size as needed, but maintaining itsratios (e.g., the ratio of the major/minor ellipse axes to each otherand the ratios of the offsets of the PTL, DTL from the origin or AOaxis), until the N1 information begins to match a boundary of thecontour line of the N2 image slice. For example, as depicted in FIG.5C3, the N1 ellipse is superimposed over the N2 image slice andpositionally coordinated with the N2 image slice via the AO axis. The N1ellipse is larger than needed to match the contour line of the N2 imageslice and is reduced in size until a portion (e.g., the PTL and P₁′ ofthe N1 ellipse) matches a portion (e.g., the most posterior point) ofthe elliptical contour line of the N2 image slice. A similar process canalso be applied to the PTL and DTL, maintaining the ratio of the PTL andDTL relative to the AO axis. As illustrated in FIG. 5C1, the N1information now corresponds to at least a portion of the damaged imageside contour line and can now be used to restore the contour line asdiscussed below with respect to FIG. 5D.

As can be understood from FIG. 5D, which is the N2 image slice of FIG.5C1 subsequent to restoration, the contour line N₂ of the N2 image slicehas been extended out to the boundaries of the ellipse 305-N1 in therestored region 402 ([block 220] of FIG. 2). This process of applyinginformation (e.g., ellipses 305 and vectors) from the reference side tothe damaged side is repeated slice-by-slice for most, if not all, imageslices 16 forming the damaged side of the femur bone model 22A. Oncemost or all of the image slices 16 of the damaged side have beenrestored, the image slices used to form the femur bone model 22A,including the recently restored images slices, are recompiled via 3Dcomputer modeling programs into a 3D femur restored bone model 28Asimilar to that depicted in FIG. 3A ([block 225] of FIG. 2).

As can be understood from FIGS. 5C1 and 5D, in one embodiment, thedamaged contour line N₂ of the N2 image slice is adjusted based on theratio of the reference side major axis major axis P₁′PP₁′ to thereference side minor axis D₁DD₁. In one embodiment, the damaged contourline N₂ of the N2 image slice is adjusted based on reference sideellipse 305-N1. Therefore, the damaged contour lines of the damaged sideimage slices can be assessed to be enlarged according to the ratiospertaining to the ellipses of the reference side image slices.

Depending on the relationship of the joint contour lines of the damagedside image slice relative to the ratios obtained from the reference sideinformation or data, the joint contour lines of the damaged side imageslice may be manipulated so the joint contour line is increased alongits major axis and/or its minor axis. Depending on the patient's kneeshape, the major axis and minor axis of the condyle ellipse varies fromperson to person. If the major axis is close to the minor axis in theundamaged condyle, then the curvature of the undamaged condyle is closeto a round shape. In such configured condyles, in the restorationprocedure, the contour of the damaged condyle can be assessed andincreased in a constant radius in both the major and minor axis. Forcondyles of other configurations, such as where the undamaged condyleshows an ellipse contour with a significantly longer major axis ascompared to its minor axis, the bone restoration may increase the majoraxis length in order to modify the damaged condyle contour.

A damaged side tibia plateau can also be restored by applying data orinformation from the reference side femur condyle to the damaged sidetibia plateau. In this continued example, the damaged side tibia plateauwill be the medial tibia plateau 306, and the reference side femurcondyle will be the lateral femur condyle 300. In one embodiment, theprocess of restoring the damaged side tibia plateau 306 begins byanalyzing the damaged side tibia plateau 306 to determine at least oneof a highest anterior point or a highest posterior point of the damagedside tibia plateau 306.

In one embodiment, as can be understood from FIG. 4C as viewed along theN4 image slice and assuming the damage to the medial tibia plateau 306is not so extensive that at least one of the highest anterior orposterior points Q4, Q4′ still exists, the damaged tibia plateau 306 canbe analyzed via tangent lines to identify the surviving high point Q4,Q4′. For example, if the damage to the medial tibia plateau 306 wasconcentrated in the posterior region such that the posterior highestpoint Q4′ no longer existed, the tangent line T_(Q4) could be used toidentify the anterior highest point Q4. Similarly, if the damage to themedial tibia plateau 306 was concentrated in the anterior region suchthat the anterior highest point Q4 no longer existed, the tangent lineT_(Q4′) could be used to identify the posterior highest point Q4′. Insome embodiments, a vector extending between the highest points Q4, Q4′may be generally perpendicular to the tangent lines T_(Q4), T_(Q4′).

In another embodiment, the reference side femur condyle ellipse 305-N1can be applied to the damaged medial tibia plateau 306 to determine atleast one of the highest anterior or posterior points Q4, Q4′ along theN4 image slice. This process may be performed assuming the damage to themedial tibia plateau 306 is not so extensive that at least one of thehighest anterior or posterior points Q4, Q4′ still exists. For example,as illustrated by FIG. 5E, which is a sagittal view of the medial tibiaplateau 306 along the N4 image slice, wherein damage 401 to the plateau306 is mainly in the posterior region, the reference side femur condyleellipse 305-N1 can be applied to the damaged medial tibia plateau 306 toidentify the anterior highest point Q4 of the tibia plateau 306.Similarly, in another example, as illustrated by FIG. 5F, which is asagittal view of the medial tibia plateau 306 along the N4 image slice,wherein damage 401 to the plateau 306 is mainly in the anterior region,the reference side femur condyle ellipse 305-N1 can be applied to thedamaged medial tibia plateau 306 to identify the posterior highest pointQ4′ of the tibia plateau 306.

In one embodiment in a manner similar to that discussed above withrespect to FIGS. 5C2 and 5C3, the reference information (e.g., N1information such as the N1 ellipse) may be applied to the damagedcontour line via the AO axis and adjusted in size (e.g., made smaller orlarger) until the N1 ellipse matches a portion of the damaged contourline in order to find the highest point, which may be, for example, Q4or Q4′. As explained above with respect to FIGS. 5C2 and 5C3, theadjustments in size for reference information may be made whilemaintaining the ratio of the N1 information.

Once the highest point is determined through any of the above-describedmethods discussed with respect to FIGS. 4C, 5E and 5F, the referenceside femur condyle vector can be applied to the damaged side tibiaplateau to determine the extent to which the tibia plateau contour line322 needs to be restored ([block 215] of FIG. 2). For example, asillustrated by FIGS. 5G and 5H, which are respectively the same views asFIGS. 5E and 5F, the vector from the reference side lateral femurcondyle 300 (e.g., the vector U₁ from the N1 image slice) is applied tothe damaged side medial tibia plateau 306 such that the vector U₁intersects the existing highest point. Thus, as shown in FIG. 5G, wherethe existing highest point is the anterior point Q4, the vector U₁ willextend through the anterior point Q4 and will spaced apart from damage401 in the posterior region of the tibia plateau contour line 322 by thedistance the posterior region of the tibia plateau contour line 322needs to be restored. Similarly, as shown in FIG. 5H, where the existinghighest point is the posterior point Q4′, the vector U₁ will extendthrough the posterior point Q4′ and will spaced apart from the damage401 of the anterior region of the tibia plateau contour line 322 by thedistance the anterior region of the tibia plateau contour line 322 needsto be restored.

As shown in FIGS. 5I and 5J, which are respectively the same views asFIGS. 5G and 5H, the damaged region 401 of the of the tibia plateaucontour line 322 is extended up to intersect the reference vector U₁,thereby restoring the missing posterior high point Q4′ in the case ofFIG. 5I and the anterior high point Q4 in the case of and FIG. 5J, therestoring resulting in restored regions 403. As can be understood fromFIGS. 5E, 5F, 5I and 5J, in one embodiment, the reference side femurcondyle ellipse 305-N1 may be applied to the damaged side tibia plateau306 to serve as a guide to locate the proper offset distance L₄ betweenthe existing high point (i.e., Q4 in FIG. 5I and Q4′ in FIG. 5I) and thenewly restored high point (i.e., Q4′ in FIG. 5I and Q4 in FIG. 5I) ofthe restored region 403. Also, in one embodiment, the reference sidefemur condyle ellipse 305-N1 may be applied to the damaged side tibiaplateau 306 to serve as a guide to achieve the proper curvature for thetibia plateau contour line 322. The curvature of the tibia plateaucontour line 322 may such that the contour line 322 near the midpointbetween the anterior and posterior high points Q4, Q4′ is offset fromthe reference vector U₁ by a distance h₄. In some embodiments, the ratioof the distances h₄/L₄ after the restoration is less than approximately0.01. As discussed above, the reference ellipse may be applied to thedamaged contour line and adjusted in size, but maintaining the ratio,until the ellipse matches a portion of the damaged contour line.

As discussed above with respect to the femur condyle image slices beingpositionally referenced to each other via a femur reference axis AO_(F),and as can be understood from FIG. 5B, each tibia image slice N1, N2,N3, N4 will be generated relative to a tibia reference axis AO_(T),which may be the same as or different from the femur reference axisAO_(F). The tibia reference axis AO_(T) will extend medial-lateral andmay pass through a center point of each area defined by the contour lineof each tibia image slice N1, N2, N3, N4. The tibia reference axisAO_(T) may extend through other regions of the tibia image slices N1,N2, N3, N4 or may extend outside of the tibia image slices, even, forexample, through the origins O₁, O₂, O₃, O₄ of the respective femurimages slices N1, N2, N3, N4 (in such a case the tibia reference axisAO_(F) and femur reference axis AO_(F) may be the same or share the samelocation).

The axis AO_(T) can be used to properly orient reference side data(e.g., the ellipse 305-N1 and vector U₁ of the N1 slice in the currentexample) when being superimposed onto a damaged side image slice (e.g.,the N4 image slice in the current example). The orientation of the dataor information of the reference side does not change as the data orinformation is being superimposed or otherwise applied to the damagedside image slice. For example, the orientation of the ellipse 305-N1 andvector U₁ of the N1 slice is maintained or held constant during thesuperimposing of such reference information onto the N4 slice such thatthe reference information does not change when being superimposed on orotherwise applied to the N4 slice. Thus, since the reference sideinformation is indexed to the damaged side image slice via the axisAO_(T) and the orientation of the reference side information does notchange in the process of being applied to the damaged side image slice,the reference side information can simply be adjusted with respect tosize to assist in the restoration of the damaged side image slice.

The contour line N₄ of the N4 image slice, as with any contour line ofany femur or tibia image slice, may be generated via an open or closedloop computer analysis of the cortical bone of the medial tibia plateau306 in the N4 image slice, thereby outlining the cortical bone with anopen or closed loop contour line N₄. Where the contour lines are closedloop, the resulting 3D models 22, 28 will be 3D volumetric models. Wherethe contour lines are open loop, the resulting 3D models 22, 28 will be3D surface models.

The preceding example discussed with respect to FIGS. 5A-5J is given inthe context of the lateral femur condyle 300 serving as the referenceside and the medial femur condyle 302 and medial tibia condyle 306 beingthe damaged sides. Specifically, reference data or information (e.g.,ellipses, vectors, etc.) from lateral femur condyle 300 is applied tothe medial femur condyle 302 and medial tibia plateau 306 for therestoration thereof. The restoration process for the contour lines ofthe damaged side femur condyle 302 and damaged side tibia plateau 306take place slice-by-slice for the image slices 16 forming the damagedside of the bone models 22A, 22B ([block 220] of FIG. 2). The restoredimage slices 16 are then utilized when a 3D computer modeling programrecompiles the image slices 16 to generate the restored bone models 28A,28B ([block 225] of FIG. 2).

While a specific example is not given to illustrate the reversedsituation, wherein the medial femur condyle 302 serves as the referenceside and the lateral femur condyle 300 and lateral tibia condyle 304 arethe damaged sides, the methodology is the same as discussed with respectto FIGS. 5A-5J and need not be discussed in such great detail. It issufficient to know that reference data or information (e.g., ellipses,vectors, etc.) from the medial femur condyle 302 is applied to thelateral femur condyle 300 and lateral tibia plateau 304 for therestoration thereof, and the process is the same as discussed withrespect to FIGS. 5A-5J.

2. Employing Vectors from a Tibia Plateau of a Reference Side of a KneeJoint to Restore the Tibia Plateau of the Damaged Side

A damaged side tibia plateau can also be restored by applying data orinformation from the reference side tibia plateau to the damaged sidetibia plateau. In this example, the damaged side tibia plateau will bethe medial tibia plateau 306, and the reference side tibia plateau willbe the lateral tibia plateau 304.

In one embodiment, the process of restoring the damaged side tibiaplateau 306 begins by analyzing the reference side tibia plateau 304 todetermine the highest anterior point and a highest posterior point ofthe reference side tibia plateau 304. Theses highest points can then beused to determine the reference vector.

In one embodiment, as can be understood from FIG. 4C as viewed along theN3 image slice, the reference side tibia plateau 304 can be analyzed viatangent lines to identify the highest points Q3, Q3′. For example,tangent line T_(Q3) can be used to identify the anterior highest pointQ3, and tangent line T_(Q3′) can be used to identify the posteriorhighest point Q3′. In some embodiments, a vector extending between thehighest points Q3, Q3′ may be generally perpendicular to the tangentlines T_(Q3), T_(Q3′).

In another embodiment, the reference side femur condyle ellipse 305-N1can be applied to the reference side lateral tibia plateau 304 todetermine the highest anterior or posterior points Q3, Q3′ along the N3image slice. For example, as can be understood from FIG. 4A, thereference side femur condyle ellipse 305-N1 (or ellipse 305-N3 ifanalyzed in the N3 image slice) can be applied to the reference sidelateral tibia plateau 304 to identify the anterior highest point Q1 ofthe tibia plateau 304, and the reference side femur condyle ellipse305-N1 (or ellipse 305-N3 if analyzed in the N3 image slice) can beapplied to the reference side lateral tibia plateau 304 to identify theposterior highest point Q1′ of the tibia plateau 306. Where the ellipse305-N3 of the N3 image slice is utilized, the highest tibia plateaupoints may be Q3, Q3′.

As can be understood from FIG. 4A, once the highest points aredetermined, a reference vector can be determined by extending a vectorthrough the points. For example, vector V₁ can be found by extending thevector through highest tibia plateau points Q1, Q1′ in the N1 slice.

In one embodiment, the process of restoring the damaged side tibiaplateau 306 continues by analyzing the damaged side tibia plateau 306 todetermine at least one of a highest anterior point or a highestposterior point of the damaged side tibia plateau 306.

In one embodiment, as can be understood from FIG. 4C as viewed along theN4 image slice and assuming the damage to the medial tibia plateau 306is not so extensive that at least one of the highest anterior orposterior points Q4, Q4′ still exists, the damaged tibia plateau 306 canbe analyzed via tangent lines to identify the surviving high point Q4,Q4′. For example, if the damage to the medial tibia plateau 306 wasconcentrated in the posterior region such that the posterior highestpoint Q4′ no longer existed, the tangent line T_(Q4) could be used toidentify the anterior highest point Q4. Similarly, if the damage to themedial tibia plateau 306 was concentrated in the anterior region suchthat the anterior highest point Q4 no longer existed, the tangent lineT_(Q4′) could be used to identify the posterior highest point Q4′.

In another embodiment, the reference side femur condyle ellipse 305-N1can be applied to the damaged medial tibia plateau 306 to determine atleast one of the highest anterior or posterior points Q4, Q4′ along theN4 image slice. This process may be performed assuming the damage to themedial tibia plateau 306 is not so extensive that at least one of thehighest anterior or posterior points Q4, Q4′ still exists. For example,as illustrated by FIG. 5E, which is a sagittal view of the medial tibiaplateau 306 along the N4 image slice, wherein damage 401 to the plateau306 is mainly in the posterior region, the reference side femur condyleellipse 305-N1 can be applied to the damaged medial tibia plateau 306 toidentify the anterior highest point Q4 of the tibia plateau 306.Similarly, in another example, as illustrated by FIG. 5F, which is asagittal view of the medial tibia plateau 306 along the N4 image slice,wherein damage 401 to the plateau 306 is mainly in the anterior region,the reference side femur condyle ellipse 305-N1 can be applied to thedamaged medial tibia plateau 306 to identify the posterior highest pointQ4′ of the tibia plateau 306.

In one embodiment in a manner similar to that discussed above withrespect to FIGS. 5C2 and 5C3, the reference information (e.g., N1information such as the N1 ellipse) may be applied to the damagedcontour line via the AO axis and adjusted in size (e.g., made smaller orlarger) until the N1 ellipse matches a portion of the damaged contourline in order to find the highest point, which may be, for example, Q4or Q4′. As explained above with respect to FIGS. 5C2 and 5C3, theadjustments in size for reference information may be made whilemaintaining the ratio of the N1 information.

Once the highest point is determined through any of the above-describedmethods discussed with respect to FIGS. 4C, 5E and 5F, the referenceside tibia plateau vector can be applied to the damaged side tibiaplateau to determine the extent to which the tibia plateau contour line322 needs to be restored ([block 215] of FIG. 2). For example, as can beunderstood from FIGS. 5K and 5L, which are respectively the same viewsas FIGS. 5G and 5H, the vector from the reference side lateral tibiaplateau 304 (e.g., the vector V₁ from the N1 image slice) is applied tothe damaged side medial tibia plateau 306 such that the vector V₁intersects the existing highest point. Thus, as shown in FIG. 5K, wherethe existing highest point is the anterior point Q4, the vector V₁ willextend through the anterior point Q4 and will spaced apart from damage401 in the posterior region of the tibia plateau contour line 322 by thedistance the posterior region of the tibia plateau contour line 322needs to be restored. Similarly, as shown in FIG. 5L, where the existinghighest point is the posterior point Q4′, the vector V₁ will extendthrough the posterior point Q4′ and will spaced apart from the damage401 of the anterior region of the tibia plateau contour line 322 by thedistance the anterior region of the tibia plateau contour line 322 needsto be restored.

As shown in FIGS. 5M and 5N, which are respectively the same views asFIGS. 5I and 5J, the damaged region 401 of the of the tibia plateaucontour line 322 is extended up to intersect the reference vector V₁,thereby restoring the missing posterior high point Q4′ in the case ofFIG. 5M and the anterior high point Q4 in the case of and FIG. 5N, therestoring resulting in restored regions 403. As can be understood fromFIGS. 5E, 5F, 5M and 5N, in one embodiment, the reference side femurcondyle ellipse 305-N1 may be applied to the damaged side tibia plateau306 to serve as a guide to locate the proper offset distance L₄ betweenthe existing high point (i.e., Q4 in FIG. 5M and Q4′ in FIG. 5N) and thenewly restored high point (i.e., Q4′ in FIG. 5M and Q4 in FIG. 5N) ofthe restored region 403. Also, in one embodiment, the reference sidefemur condyle ellipse 305-N1 may be applied to the damaged side tibiaplateau 306 to serve as a guide to achieve the proper curvature for thetibia plateau contour line 322. The curvature of the tibia plateaucontour line 322 may such that the contour line 322 near the midpointbetween the anterior and posterior high points Q4, Q4′ is offset fromthe reference vector U₁ by a distance h₄. In some embodiments, the ratioof the distances h₄/L₄ after the restoration is less than approximately0.01. As discussed above, the reference ellipse may be applied to thedamaged contour line and adjusted in size, but maintaining the ratio,until the ellipse matches a portion of the damaged contour line.

As discussed above with respect to the femur condyle image slices beingpositionally referenced to each other via a femur reference axis AO_(F),and as can be understood from FIG. 5B, each tibia image slice N1, N2,N3, N4 will be generated relative to a tibia reference axis AO_(T),which may be the same as or different from the femur reference axisAO_(F). The tibia reference axis AO_(T) will extend medial-lateral andmay pass through a center point of each area defined by the contour lineof each tibia image slice N1, N2, N3, N4. The tibia reference axisAO_(T) may extend through other regions of the tibia image slices N1,N2, N3, N4 or may extend outside of the tibia image slices, even, forexample, through the origins O₁, O₂, O₃, O₄ of the respective femurimages slices N1, N2, N3, N4 (in such a case the tibia reference axisAO_(F) and femur reference axis AO_(F) may be the same or share the samelocation).

The axis AO_(T) can be used to properly orient reference side data(e.g., the ellipse 305-N1 and vector V₁ of the N1 slice in the currentexample) when being superimposed onto a damaged side image slice (e.g.,the N4 image slice in the current example). The orientation of the dataor information of the reference side does not change as the data orinformation is being superimposed or otherwise applied to the damagedside image slice. For example, the orientation of the ellipse 305-N1 andvector V₁ of the N1 slice is maintained or held constant during thesuperimposing of such reference information onto the N4 slice such thatthe reference information does not change when being superimposed on orotherwise applied to the N4 slice. Thus, since the reference sideinformation is indexed to the damaged side image slice via the axisAO_(T) and the orientation of the reference side information does notchange in the process of being applied to the damaged side image slice,the reference side information can simply be adjusted with respect tosize to assist in the restoration of the damaged side image slice.

The contour line N₄ of the N4 image slice, as with any contour line ofany femur or tibia image slice, may be generated via an open or closedloop computer analysis of the cortical bone of the medial tibia plateau306 in the N4 image slice, thereby outlining the cortical bone with anopen or closed loop contour line N₄. Where the contour lines are closedloop, the resulting 3D models 22, 28 will be 3D volumetric models. Wherethe contour lines are open loop, the resulting 3D models 22, 28 will be3D surface models.

In the current example discussed with respect to FIGS. 5K-5N, theinformation from the reference side tibia plateau 304 is employed torestore the damaged side tibia plateau 306. However, the informationfrom the reference side femur condyle 300 is still used to restore thedamaged side femur condyle 302 as discussed above in the precedingexample with respect to FIGS. 5A-5D.

The preceding example discussed with respect to FIGS. 5K-5N is given inthe context of the lateral tibia plateau 304 and lateral femur condyle300 serving as the reference sides and the medial femur condyle 302 andmedial tibia condyle 306 being the damaged sides. Specifically,reference data or information (e.g., vectors from the lateral tibiaplateau 304 and ellipses, vectors, etc. from the lateral femur condyle300) are applied to the medial femur condyle 302 and medial tibiaplateau 306 for the restoration thereof. The restoration process for thecontour lines of the damaged side femur condyle 302 and damaged sidetibia plateau 306 take place slice-by-slice for the image slices 16forming the damaged side of the bone models 22A, 22B ([block 220] ofFIG. 2). The restored image slices 16 are then utilized when a 3Dcomputer modeling program recompiles the image slices 16 to generate therestored bone models 28A, 28B ([block 225] of FIG. 2).

While a specific example is not given to illustrate the reversedsituation, wherein the medial tibia plateau 306 and medial femur condyle302 serve as the reference sides and the lateral femur condyle 300 andlateral tibia condyle 304 are the damaged sides, the methodology is thesame as discussed with respect to FIGS. 5A-5D and 5K-5N and need not bediscussed in such great detail. It is sufficient to know that referencedata or information (e.g., ellipses, vectors, etc.) from the medialtibia plateau 306 and medial femur condyle 302 are applied to thelateral femur condyle 300 and lateral tibia plateau 304 for therestoration thereof, and the process is the same as discussed withrespect to FIGS. 5A-5D and 5K-5N.

e. Verifying Accuracy of Restored Bone Model

Once the bone models 22A, 22B are restored into restored bone models28A, 28B as discussed in the preceding sections, the accuracy of thebone restoration process is checked ([block 230] of FIG. 2). Beforediscussion example methodology of conducting such accuracy checks, thefollowing discussion regarding the kinetics surround a knee joint isprovided.

The morphological shape of the distal femur and its relation to theproximal tibia and the patella suggests the kinetics of the knee (e.g.,see Eckhoff et al., “Three-Dimensional Mechanics, Kinetics, andMorphology of the Knee in Virtual Reality”, JBJS (2005); 87:71-80). Themovements that occur at the knee joint are flexion and extension, withsome slight amount of rotation in the bent position. During themovement, the points of contact of the femur with the tibia areconstantly changing. Thus, in the flexed position (90° knee extension),the hinder part of the articular surface of the tibia is in contact withthe rounded back part of the femoral condyles. In the semiflexedposition, the middle parts of the tibia facets articulate with theanterior rounded part of the femoral condyles. In the fully extendedposition (0° knee extension), the anterior and the middle parts of thetibia facets are in contact with the anterior flattened portion of thefemoral condyles.

With respect to the patella, in extreme flexion, the inner articularfacet rests on the outer part of the internal condyle of the femur. Inflexion, the upper part of facets rest on the lower part of thetrochlear surface of the femur. In mid-flexion, the middle pair rest onthe middle of the trochlear surface. However, in extension, the lowerpair of facets on the patella rest on the upper portion of the trochlearsurface of the femur. The difference may be described as the shifting ofthe points of contact of the articulate surface.

The traditional knee replacement studies focus mainly around thetibial-femoral joint. The methods disclosed herein employ the patella ina tri-compartmental joint study by locating the patella groove of theknee. The posterior surface of patella presents a smooth oval articulararea divided into two facets by a vertical ridge, the facets forming themedial and lateral parts of the same surface.

The vertical ridge of the posterior patella corresponds to the femoraltrochlear groove. In the knee flexion/extension motion movement, thepatella normally moves up and down in the femoral trochlear grove alongthe vertical ridge and generates quadriceps forces on the tibia. Thepatellofemoral joint and the movement of the femoral condyles play amajor role in the primary structure/mechanics across the joint. When theknee is moving and not fully extended, the femoral condyle surfaces bearvery high load or forces. In a normal knee, the patella vertical ridgeis properly aligned along the femoral trochlear groove so this alignmentprovides easy force generation in the sliding movement. If the patellais not properly aligned along the trochlear groove or tilted in certainangles, then it is hard to initiate the sliding movement so it causesdifficulty with respect to walking. Further, the misaligned axis alongthe trochlear groove can cause dislocation of the patella on thetrochlear groove, and uneven load damage on the patella as well.

The methods disclosed herein for the verification of the accuracy of thebone restoration process employ a “trochlear groove axis” or the“trochlear groove reference plane” as discussed below. This axis orreference plane extend across the lowest extremity of trochlear groovein both the fully-extended and 90° extension of the knee. Moreover, inrelation to the joint line, the trochlear groove axis is perpendicularor generally perpendicular to the joint line of the knee.

Because the vertical ridge of the posterior patella is generallystraight (vertical) in the sliding motion, the corresponding trochleargroove axis should be straight as well. The trochlear groove axis isapplied into the theory that the joint line of the knee is parallel tothe ground. In a properly aligned knee or normal knee, the trochleargroove axis is presumed to be perpendicular or nearly perpendicular tothe joint line.

For the OA, rarely is there bone damage in the trochlear groove,typically only cartilage damage. Thus, the femoral trochlear groove canserve as a reliable bone axis reference for the verification of theaccuracy of the bone restoration when restoring a bone model 22 into arestored bone model 28.

For a detailed discussion of the methods for verifying the accuracy ofthe bone restoration process, reference is made to FIGS. 6A-6D. FIG. 6Ais a sagittal view of a femur restored bone model 28A illustrating theorders and orientations of imaging slices 16 (e.g., MRI slices, CTslices, etc.) forming the femur restored bone model 28A. FIG. 6B is thedistal images slices 1-5 taken along section lines 1-5 of the femurrestored bone model 28A in FIG. 6A. FIG. 6C is the coronal images slices6-8 taken along section lines 6-8 of the femur restored bone model 28Ain FIG. 6A. FIG. 6D is a perspective view of the distal end of the femurrestored bone model 28A.

As shown in FIG. 6A, a multitude of image slices are compiled into thefemur restored bone model 28A from the image slices originally formingthe femur bone model 22A and those restored image slices modified viathe above-described methods. Image slices may extend medial-lateral inplanes that would be normal to the longitudinal axis of the femur, suchas image slices 1-5. Image slices may extend medial-lateral in planesthat would be parallel to the longitudinal axis of the femur, such asimage slices 6-8. The number of image slices may vary from 1-50 and maybe spaced apart in a 2 mm spacing.

As shown in FIG. 6B, each of the slices 1-5 can be aligned verticallyalong the trochlear groove, wherein points G1, G2, G3, G4, G5respectively represent the lowest extremity of trochlear groove for eachslice 1-5. By connecting the various points G1, G2, G3, G4, G5, a pointO can be obtained. As can be understood from FIGS. 3B and 6D, resultingline GO is perpendicular or nearly perpendicular to tangent line P₁P₂.In a 90° knee extension in FIG. 3B, line GO is perpendicular or nearlyperpendicular to the joint line of the knee and line P₁P₂.

As shown in FIG. 6C, each of the slices 6-8 can be aligned verticallyalong the trochlear groove, wherein points H6, H7, H8 respectivelyrepresent the lowest extremity of the trochlear groove for each slice6-8. By connecting the various points H6, H7, H8, the point O can againbe obtained. As can be understood from FIGS. 3A and 6D, resulting lineHO is perpendicular or nearly perpendicular to tangent line D₁D₂. In a0° knee extension in FIG. 3A, line HO is perpendicular or nearlyperpendicular to the joint line of the knee and line D₁D₂.

As illustrated in FIG. 6D, the verification of the accuracy of therestoration process includes determining if the reference lines GO andHO are within certain tolerances with respect to being parallel tocertain lines and perpendicular to certain lines. The line GO, as thereference across the most distal extremity of the trochlear groove ofthe femur and in a 90° knee extension, should be perpendicular totangent line D₁D₂ The line HO, as the reference across the mostposterior extremity of trochlear groove of the femur and in a 0° kneeextension, should be perpendicular to tangent line P₁P₂.

Line HO and line P₁P₂ may form a plane S, and lines GO and line D₁D₂ mayform a plane P that is perpendicular to plane S and forms line SRtherewith. Line HO and line GO are parallel or nearly parallel to eachother. Lines P₁P₂, D₁D₂ and SR are parallel or nearly parallel to eachother. Lines P₁P₂, D₁D₂ and SR are perpendicular or nearly perpendicularto lines HO and GO.

As can be understood from FIG. 6D, in one embodiment, lines HO and GOmust be within approximately three degrees of being perpendicular withlines P₁P₂, and D₁D₂ or the restored bones models 28A, 28B will berejected and the restoration process will have to be repeated until theresulting restored bone models 28A, 28B meet the stated tolerances, orthere has been multiple failed attempts to meet the tolerances ([block230] [block 240] of FIG. 2). Alternatively, as can be understood fromFIG. 6D, in another embodiment, lines HO and GO must be withinapproximately six degrees of being perpendicular with lines P₁P₂, andD₁D₂ or the restored bones models 28A, 28B will be rejected and therestoration process will have to be repeated until the resultingrestored bone models 28A, 28B meet the stated tolerances, or there hasbeen multiple failed attempts to meet the tolerances ([block 230]-[block240] of FIG. 2). If multiple attempts to provide restored bone models28A, 28B satisfying the tolerances have been made without success, thenbone restoration reference data may be obtained from another similarjoint that is sufficiently free of deterioration. For example, in thecontext of knees, if repeated attempts have been made without success torestore a right knee medial femur condyle and tibia plateau fromreference information obtained from the right knee lateral sides, thenreference data could be obtained from the left knee lateral or medialsides for use in the restoration process in a manner similar todescribed above.

In some embodiments, as depicted in the table illustrated in FIG. 7,some OA knee conditions are more likely to be restored via the methodsdisclosed herein than other conditions when it comes to obtaining thereference data from the same knee as being restored via the referencedata. For example, the damaged side of the knee may be light (e.g., nobone damage or bone damage less than 1 mm), medium (e.g., bone damage ofapproximately 1 mm) or severe (e.g., bone damage of greater than 1 mm).As can be understood from FIG. 7, the bone restoration provided via someof the above-described embodiments may apply to most OA patients havinglight-damaged knees and medium-damaged knees and some OA patients havingsevere-damaged knees, wherein restoration data is obtained from areference side of the knee having the damaged side to be restored.However, for most OA patients having severe-damaged and some OA patientshaving medium-damaged knees, in some embodiments as described below,bone restoration analysis entails obtaining restoration data from a goodfirst knee of the patient for application to, and restoration of, a badsecond knee of the patient.

It should be understood that the indications represented in the table ofFIG. 7 are generalities for some embodiments disclosed herein withrespect to some patients and should not be considered as absoluteindications of success or failure with respect to whether or not any oneor more of the embodiments disclosed herein may be successfully appliedto an individual patient having any one of the conditions (light,medium, severe) reflected in the table of FIG. 7. Therefore, the tableof FIG. 7 should not be considered to limit any of the embodimentsdisclose herein.

f. Further Discussion of Bone Model Restoration Methods

For further discussion regarding embodiments of bone model restorationmethods, reference is made to FIGS. 8A-8D. FIG. 8A shows theconstruction of reference line SQ in a medial portion of the tibiaplateau. In one embodiment, the reference line SQ may be determined bysuperimposing an undamaged femoral condyle ellipse onto the medial tibiaplateau to obtain two tangent points Q and S. In another embodiment, thetangent points Q and S may be located from the image slices byidentifying the highest points at the posterior and anterior edges ofthe medial tibia plateau. By identifying tangent points Q and S, thetangent lines QP and SR may be determined by extending lines across eachof the tangent points Q and S, wherein the tangent lines QP and SR arerespectively tangent to the anterior and posterior curves of the medialtibia plateau. Reference line SQ may be obtained where tangent line QPis perpendicular or generally perpendicular to reference line SQ andtangent line SR is perpendicular or generally perpendicular to referenceline SQ.

FIG. 8B shows the restoration of a damaged anterior portion of thelateral tibia plateau. The reference vector line or the vector plane isobtained from FIG. 8A, as line SQ or plane SQ. The reference vectorplane SQ from the medial side may be applied as the reference plane inthe damaged lateral side of the tibia plateau surface. In FIG. 8B, thecontour of the damaged anterior portion of the lateral tibia plateau maybe adjusted to touch the proximity of the reference vector plane SQ fromthe undamaged medial side. That is, points S′ and Q′ are adjusted toreach the proximity of the plane SQ. The outline between points S′ andQ′ are adjusted and raised to the reference plane SQ. By doing thisadjustment, a restored tangent point Q′ may be obtained via this vectorplane SQ reference.

As shown in FIG. 8D, the reference vector plane SQ in the medial side isparallel or nearly parallel to the restored vector plane S′Q′ in thelateral side. In FIG. 8B, the length L″ represents the length of lineS′Q′. The length l″ is the offset from the recessed surface region ofthe tibia plateau to the plane S′Q′ after the restoration. In the bonerestoration assessment, the ratio of l″/L″ may be controlled to be lessthan 0.01.

FIG. 8C is the coronal view of the restored tibia after 3Dreconstruction, with a 0° knee extension model. The points U and Vrepresent the lowest extremity of tangent contact points on each of thelateral and medial tibia plateau, respectively. In one embodiment,tangent points U and V are located within the region between the tibiaspine and the medial and lateral epicondyle edges of the tibia plateau,where the slopes of tangent lines in this region are steady andconstant. In one embodiment, the tangent point U in the lateral plateauis in area I between the lateral side of lateral intercondylar tubercleto the attachment of the lateral collateral ligament. For the medialportion, the tangent point V is in area II between the medial side ofmedial intercondylar tubercle to the medial condyle of tibia, as shownin FIG. 8C.

As previously stated, FIG. 8C represents the restored tibia models and,therefore, the reference lines N1 and N2 can apply to the restored tibiamodel in FIG. 8C, when the knee is at 0° extension. As can be understoodfrom FIG. 8C, line N1 when extended across point U is perpendicular orgenerally perpendicular to line-UV, while line N2 when extended acrosspoint V is perpendicular or generally perpendicular to line UV. Inrestored the tibia model, line UV may be parallel or nearly parallel tothe joint line of the knee. Within all these reference lines, in oneembodiment, the tolerable range of the acute angle between nearlyperpendicular or nearly parallel lines or planes may be within anabsolute 6-degree angle, |X˜X′|≤6°. If the acute angle difference fromFIG. 8C is less than 6°, the numerical data for the femur and/or tibiarestoration is acceptable. This data may be transferred to the furtherassess the varus/valgus alignment of the knee models.

FIG. 9A is a coronal view of the restored knee models of proximal femurand distal tibia with 0° extension of the knee. Line ab extends acrossthe lowest extremity of trochlear groove of the distal femur model.Reference lines N1 and N2 are applied to the restored knee model ofvarus/valgus alignment, where line-N1 is parallel or generally parallelto line N2 and line ab. Depending on the embodiment, the acute anglesbetween these lines may be controlled within a 3 degree range or a 5degree range. The tangent points D and E represent the lowestextremities of the restored proximal femur model. The tangent points Uand V are obtained from the restored distal tibia plateau surface. Inthe medial portion, t1′ represents the offset of the tangent linesbetween the medial condyle and medial tibia plateau. In the lateralportion, t2′ represents the offset of the tangent lines between thelateral condyle and lateral tibia plateau. In the varus/valgus rotationand alignment, t1′ is substantially equal to t2′, or |t1′−t2′|<<1 mm.Therefore, line DE may be generally parallel to the joint line of theknee and generally parallel to line UV.

FIG. 9B is a sagittal view of the restored knee models. Line 348represents the attachment location of lateral collateral ligament whichlies on the lateral side of the joint. Line 342 represents the posteriorextremity portion of the lateral femoral condyle. Line 344 representsthe distal extremity portion of the lateral condyle. In this restoredknee model, line 344 may be parallel or generally parallel to line L.That is, plane 344 is parallel or generally parallel to plane L andparallel or generally parallel to the joint plane of the knee. In oneembodiment, the tolerable range of acute angle between these planes maybe controlled within an absolute 6 degrees. If the angle is less than anabsolute 6 degrees, the information of the femur and tibia model willthen be forwarded to the preoperative design for the implant modeling.If the acute angle is equal or larger than an absolute 6 degrees, theimages and 3D models will be rejected. In this situation, the procedurewill be returned to start all over from the assessment procedure ofreference lines/planes.

g. Using Reference Information from a Good Joint to Create a RestoredBone Model for a Damaged Joint

As mentioned above with respect to the table of FIG. 7, the knee that isthe target of the arthroplasty procedure may be sufficiently damaged onboth the medial and lateral sides such that neither side may adequatelyserve as a reference side for the restoration of the other side. In afirst embodiment and in a manner similar to that discussed above withrespect to FIGS. 2-6D, reference data for the restoration of thedeteriorated side of the target knee may be obtained from the patient'sother knee, which is often a healthy knee or at least has a healthy sidefrom which to obtain reference information. In a second embodiment, theimage slices of the healthy knee are reversed in a mirrored orientationand compiled into a restored bone model representative of thedeteriorated knee prior to deterioration, assuming the patient's twoknees where generally mirror images of each other when they were bothhealthy. These two embodiments, which are discussed below in greaterdetail, may be employed when the knee targeted for arthroplasty issufficiently damaged to preclude restoration in a manner similar to thatdescribed above with respect to FIGS. 2-6D. However, it should be notedthat the two embodiments discussed below may also be used in place of,or in addition to, the methods discussed above with respect to FIGS.2-6D, even if the knee targeted for arthroplasty has a side that issufficiently healthy to allow the methods discussed above with respectto FIGS. 2-6D to be employed.

For a discussion of the two embodiments for creating a restored bonemodel for a deteriorated knee targeted for arthroplasty from imageslices obtained from a healthy knee, reference is made to FIGS. 10A and10B. FIG. 10A is a diagram illustrating the condition of a patient'sright knee, which is in a deteriorated state, and left knee, which isgenerally healthy. FIG. 10B is a diagram illustrating the twoembodiments. While in FIGS. 10A and 10B and the following discussion theright knee 702 of the patient 700 is designated as the deteriorate knee702 and the left knee 704 of the patient 700 is designated as thehealthy knee 704, of course such designations are for example purposesonly and the conditions of the knees could be the reverse.

As indicated in FIG. 10A, the patient 700 has a deteriorated right knee702 formed of a femur 703 and a tibia 707 and which has one or both ofsides in a deteriorated condition. In this example, the lateral side 705of the right knee 702 is generally healthy and the medial side 706 ofthe right knee 702 is deteriorated such that the right medial condyle708 and right medial tibia plateau 710 will need to be restored in anyresulting restored bone model 28. As can be understood from FIG. 10A,the patient also has a left knee 704 that is also formed of a femur 711and a tibia 712 and which has a medial side 713 and a lateral side 714.In FIG. 10A, both sides 713, 714 of the left knee 704 are generallyhealthy, although, for one of the following embodiments, a singlehealthy side is sufficient to generate a restored bone model 28 for theright knee 702.

As indicated in FIG. 10B, image slices 16 of the deteriorated right knee702 and healthy left knee 704 are generated as discussed above withrespect to FIGS. 1A and 1B. In the first embodiment, which is similar tothe process discussed above with respect to FIGS. 2-6D, except theprocess takes place with a deteriorated knee and a health knee asopposed to the deteriorated and healthy sides of the same knee,reference information (e.g., vectors, lines, planes, ellipses, etc. asdiscussed with respect to FIGS. 2-6D) 720 is obtained from a healthyside of the healthy left knee 704 [block 1000 of FIG. 10B]. Thereference information 720 obtained from the image slices 16 of thehealth left knee 704 is applied to the deteriorated sides of the rightknee 702 [block 1005 of FIG. 10B]. Specifically, the applied referenceinformation 720 is used to modify the contour lines of the images slices16 of the deteriorated sides of the right knee 702, after which themodified contour lines are compiled, resulting in a restored bone model28 that may be employed as described with respect to FIG. 1C. Thereference information 720 obtained from the healthy left knee imageslices 16 may be coordinated with respect to position and orientationwith the contour lines of the deteriorated right knee image slices 16 byidentifying a similar location or feature on each knee joint that isgenerally identical between the knees and free of bone deterioration,such as a point or axis of the femur trochlear groove or tibia plateauspine.

In the second embodiment, image slices 16 are generated of both thedeteriorate right knee 702 and healthy left knee 704 as discussed abovewith respect to FIG. 1B. The image slices 16 of the deteriorated rightknee 702 may be used to generate the arthritic model 36 as discussedabove with respect to FIG. 1D. The image slices 16 of the healthy leftknee 704 are mirrored medially/laterally to reverse the order of theimage slices 16 [block 2000 of FIG. 10B]. The mirrored/reversed orderimage slices 16 of the healthy left knee 704 are compiled, resulting ina restored bone model 28 for the right knee 702 that is formed from theimage slices 16 of the left knee 704 [block 2000 of FIG. 10B]. In otherwords, as can be understood from [block 2000] and its associatedpictures in FIG. 10B, by medially/laterally mirroring the image slices16 of left knee 704 to medially/laterally reverse their order and thencompiling them in such a reversed order, the image slices 16 of the leftknee 704 may be formed into a bone model that would appear to be a bonemodel of the right knee 702 in a restored condition, assuming the rightand left knees 702, 704 were generally symmetrically identical mirrorimages of each other when both were in a non-deteriorated state.

To allow for the merger of information (e.g., saw cut and drill holedata 44 and jig data 46) determined respectively from the restored bonemodel 28 and the arthritic model 28 as discussed above with respect toFIG. 1E, the restored bone model 28 generated from the mirrored imageslices 16 of the healthy left knee 704 may be coordinated with respectto position and orientation with the arthritic model 36 generated fromthe image slices 16 of the deteriorated right knee 702. In oneembodiment, this coordination between the models 28, 36 may be achievedby identifying a similar location or feature on each knee joint that isgenerally identical between the knees and free of bone deterioration,such as a point or axis of the femur trochlear groove or tibia plateauspine. Such a point may serve as the coordination or reference point P′(X_(0-k), Y_(0-k), Z_(0-k)) as discussed with respect to FIG. 1E.

While the two immediately preceding embodiments are discussed in thecontext of knee joints, these embodiments, like the rest of theembodiments disclosed throughout this Detailed Description, are readilyapplicable to other types of joints including ankle joints, hip joints,wrist joints, elbow joints, shoulder joints, finger joints, toe joints,etc., and vertebrae/vertebrae interfaces and vertebrae/skull interfaces.Consequently, the content of this Detailed Description should not beinterpreted as being limited to knees, but should be consider toencompass all types of joints and bone interfaces, without limitation.

Although the present invention has been described with reference topreferred embodiments, persons skilled in the art will recognize thatchanges may be made in form and detail without departing from the spiritand scope of the invention.

The invention claimed is:
 1. A method of planning and performing anarthroplasty of a knee joint that has assumed a degenerated state, thearthroplasty being planned to achieve a post-surgical alignment of theknee joint that is a natural alignment of the knee joint thathypothetically existed prior to the knee joint assuming the degeneratedstate, the method comprising: accessing on a computer degenerated imagedata of a first bone of the knee joint, the degenerated image datareflecting the first bone in the degenerated state, the degeneratedimage data including a degenerated portion and a reference portion, thedegenerated portion representing a degenerated condyle of the firstbone, the reference portion representing a reference condyle of thefirst bone, the degenerated condyle being more degenerated than thereference condyle; modifying with the computer the degenerated imagedata by adjusting the degenerated portion in view of the referenceportion, the modifying of the degenerated image data resulting inrestored image data of the first bone, the restored image datareflecting the first bone in a less degenerated state as compared to thedegenerated image data reflecting the first bone in the degeneratedstate; generating with the computer a three-dimensional restored bonemodel from the restored image data of the first bone, thethree-dimensional restored bone model reflecting the first bone in theless degenerated state; computer defining a resection of the first bonethat allows a prosthetic implanted on the first bone to achieve thepost-surgical alignment of the knee joint that is the natural alignment,the computer defining including aligning condylar surfaces of a computermodel of the prosthetic with corresponding surfaces of thethree-dimensional restored bone model reflecting the first bone in theless degenerated state; computer referencing with respect to locationand orientation in a three dimensional computer coordinate system thedefined resection with a registration surface defined on a degeneratedcomputer model of the first bone in the degenerated state, thedegenerated computer model of the first bone including, or being aproduct of, the degenerated image data; and contacting the first bone ofthe knee joint at a location corresponding to the registration surfaceand resecting the bone according to the defined resection, thecontacting registering the defined resection with the first bone.
 2. Themethod of claim 1, wherein the computer defining further includessuperimposing the computer model of the prosthetic and thethree-dimensional restored bone model reflecting the first bone in theless degenerated state.
 3. A method of planning and performing anarthroplasty of a knee joint that has assumed a degenerated state, thearthroplasty being planned to achieve a post-surgical alignment of theknee joint that is a natural alignment of the knee joint thathypothetically existed prior to the knee joint assuming the degeneratedstate, the method comprising: accessing on a computer degenerated imagedata of a first bone of the knee joint, the degenerated image datareflecting the first bone in the degenerated state, the degeneratedimage data including a degenerated portion and a reference portion, thedegenerated portion representing a degenerated condyle of the firstbone, the reference portion representing a reference condyle of thefirst bone, the degenerated condyle being more degenerated than thereference condyle; modifying with the computer the degenerated imagedata by adjusting the degenerated portion in view of the referenceportion, the modifying of the degenerated image data resulting inrestored image data of the first bone, the restored image datareflecting the first bone in a less degenerated state as compared to thedegenerated image data reflecting the first bone in the degeneratedstate; generating with the computer a three-dimensional restored bonemodel from the restored image data of the first bone, thethree-dimensional restored bone model reflecting the first bone in theless degenerated state; defining a resection of the first bone thatallows a prosthetic implanted on the first bone to achieve thepost-surgical alignment of the knee joint that is the natural alignment,the computer defining including superimposing a computer model of theprosthetic and the three-dimensional restored bone model reflecting thefirst bone in the less degenerated state; computer referencing withrespect to location and orientation in a three dimensional computercoordinate system the defined resection with a registration surfacedefined on a degenerated computer model of the first bone in thedegenerated state, the degenerated computer model of the first boneincluding, or being a product of, the degenerated image data; andcontacting the first bone of the knee joint at a location correspondingto the registration surface and resecting the bone according to thedefined resection, the contacting registering the defined resection withthe first bone.
 4. A method of manufacturing a custom arthroplasty jigfor use in an arthroplasty of a knee joint that has assumed adegenerated state, the arthroplasty being planned to achieve apost-surgical alignment of the knee joint that is a natural alignment ofthe knee joint that hypothetically existed prior to the knee jointassuming the degenerated state, the method comprising: accessing on acomputer degenerated image data of a first bone of the knee joint, thedegenerated image data reflecting the first bone in the degeneratedstate, the degenerated image data including a degenerated portion and areference portion, the degenerated portion representing a degeneratedcondyle of the first bone, the reference portion representing areference condyle of the first bone, the degenerated condyle being moredegenerated than the reference condyle; modifying with the computer thedegenerated image data by adjusting the degenerated portion in view ofthe reference portion, the modifying of the degenerated image dataresulting in restored image data of the first bone, the restored imagedata reflecting the first bone in a less degenerated state as comparedto the degenerated image data reflecting the first bone in thedegenerated state; generating with the computer a three-dimensionalrestored bone model from the restored image data of the first bone, thethree-dimensional restored bone model reflecting the first bone in theless degenerated state; computer defining a resection of the first bonethat allows a prosthetic implanted on the first bone to achieve thepost-surgical alignment of the knee joint that is the natural alignment,the computer defining including aligning condylar surfaces of a computermodel of the prosthetic with corresponding surfaces of thethree-dimensional restored bone model reflecting the first bone in theless degenerated state; computer referencing with respect to locationand orientation in a three dimensional computer coordinate system thedefined resection with a registration surface defined on a degeneratedcomputer model of the first bone in the degenerated state, thedegenerated computer model of the first bone including, or being aproduct of, the degenerated image data; and manufacturing the customarthroplasty jig to have a resection guide and a custom mating surfacedefined according to the resection and the registration surface,respectively.
 5. The method of claim 1, wherein the reference portion ofthe degenerated image data includes a condyle contour of the referencecondyle and the degenerated portion of the degenerated image dataincludes a condyle contour of the degenerated condyle.
 6. The method ofclaim 5, wherein computer modifying the degenerated image data byadjusting the degenerated portion in view of the reference portionincludes: determining a reference vector from the condyle contour of thereference condyle; applying the reference vector to the condyle contourof the degenerated condyle; and causing the condyle contour of thedegenerated condyle to extend to the reference vector.
 7. The method ofclaim 6, wherein the reference vector is associated with a femoralcondyle ellipse of the condyle contour of the reference condyle.
 8. Themethod of claim 7, wherein the femoral condyle ellipse is determined viaa femoral sagittal image slice taken near a femoral condyle point thatis at least one of the most distal femoral condylar contact point whenthe knee joint is in zero degree extension or the most posterior femoralcondylar point when the knee joint is in 90 degree extension.
 9. Themethod of claim 8, wherein the reference vector corresponds to the majoraxis of the femoral condyle ellipse.
 10. The method of claim 6, whereinthe reference vector is associated with highest tibial anterior andposterior points of the condyle contour of the reference condyle. 11.The method of claim 6, further comprising verify an accuracy ofmodifying the degenerated image data by comparing an axis extendingalong a trochlear groove of the restored image data to a joint line ofthe restored image data.
 12. The method of claim 11, wherein theaccuracy is acceptable wherein the axis extending along the trochleargroove and the joint line are within approximately six degrees of beingperpendicular.
 13. The method of claim 1, wherein the degenerated imagedata includes image contour lines determined from MRI or CT images takenof the first bone.
 14. The method of claim 1, wherein the restored imagedata includes two-dimensional contour lines.